Rash

There are many causes of skin rashes.

Rash is a general, nonspecific term that describes any visible skin outbreak. Rashes are very common in all ages, from infants to seniors, and nearly everyone will have some type of rash at some point in their life. There are a wide variety of medical diagnoses for skin rashes and many different causes. It is not possible to fully cover every type of rash in this type of article. Therefore, special mention has been given here to some of the most common types of rashes. A dermatologist is a medical provider who specializes in diseases of the skin and may need to be consulted for rashes that are difficult to diagnose and treat.

Some dermatologists have reported cases of so-called "COVID toe" in both adults and children. Some patients found it painful when their toes were pressed, and others did not.

Rashes may be divided into two types: infectious or noninfectious.

While there are many different types, rashes may basically be divided into two types: infectious or noninfectious.

Noninfectious rashes include eczema, contact dermatitis, psoriasis, seborrheic dermatitis, drug eruptions, rosacea, hives (urticaria), dry skin (xerosis), and allergic dermatitis. Many noninfectious rashes are typically treated with corticosteroid creams and/or pills. Even a noncontagious, noninfectious rash can cause discomfort and anxiety.

Infection-associated rashes, such as ringworm (tinea), impetigo, Staphylococcus, scabies, herpes, chickenpox, and shingles, are treated by treating the underlying cause. Infectious agents that can cause a rash include viruses, bacteria, fungi, and parasites.

Determining the specific cause of rash usually requires a description of the skin rash, including its shape, arrangement, distribution, duration, symptoms, and history. All of these factors are important in identifying the correct diagnosis. Accurate information about past treatments, successful and unsuccessful, is very important. Treatments that work may be a clue to the cause of the rash, may mask symptoms, or change the appearance, making a definite diagnosis harder. Sometimes good quality pictures of an earlier stage of the rash may aid diagnosis.

Many different risk factors determine what rash or rashes a patient might get. A family history of eczema, frequent exposure to sick children, necessary use of immunosuppressive medications, and exposure to multiple medications all increase the risk of developing rashes.

A careful drug history that includes over-the-counter (OTC) medications, supplements, and prescription drugs such as birth control pills is also important. The timing of when medications are started and stops may provide important clues for establishing the cause of a rash.

There are some rashes that only appear in association with pregnancy, either during pregnancy or even after the delivery of the baby. Most of these are not serious but can be very irritating.

The reported history will help characterize the duration, onset, relationship to various environmental factors, skin symptoms (such as itching and pain), and constitutional symptoms such as fever, headache, and chills. Based on the health care provider's initial impression of a rash, treatment may be started. The treatment may need to be modified pending various laboratory and special skin examinations.

Trichophyton is a type of skin fungus that causes skin rash (tinea or ringworm).

Skin rashes have an exhaustive list of potential causes, including infections. In a broad sense, rashes are commonly categorized as infectious or noninfectious.

Causes of infectious rashes include:

Fungal

• Trichophyton is a type of skin fungus that commonly causes rashes of the skin, hair, and nails. This infectious rash is called tinea or ringworm. It may occur on any body surface.
• Candida can cause common yeast infections in moist areas like between the fingers, in the mouth, vaginal area, and also in the groin folds. It would be unusual to have a Candida rash in a dry body area.
• Other much less common fungal infections include cryptococcosis, aspergillosis, and histoplasmosis. These are fairly uncommon in healthy people and are more frequently seen in individuals with a compromised immune system as in HIV/AIDS, immune suppression due to cancer chemotherapy, and patients on long-term immunosuppression because of organ transplant or hematologic diseases.

Viral

• Herpes simplex (HSV) types I and II may cause infections of the lips, nose, facial skin, genitals, and buttocks. HSV infections may also cause erythema multiforme (minor), which is characterized by tender bull's eye-like targets on the palms, usually corresponding to an HSV flare.
• Herpes zoster causes chickenpox and shingles.
• HIV causes many types of rashes, both nonspecific viral reactions as well as infection-associated rashes. There is also an increased rate of noninfectious drug rashes in those receiving medical therapy for HIV.
• Epstein-Barr virus (EBV) is associated with many types of rashes and most commonly with mononucleosis ("mono" or "kissing disease"). This may occur in any patient but especially in those given penicillin family medications such as ampicillin or amoxicillin.
• Many other viruses, including parvovirus and enteroviruses like echoviruses or coxsackievirus, cause rashes. Coxsackievirus is associated with hand, foot, and mouth disease (HFMD). Parvovirus infections can cause a variety of rashes ranging from red cheeks to a net-like red rash on the arms to purple hands and feet. Young children are particularly prone to many kinds of viral infections and illnesses.
• Erythema multiforme causes small target-like circles on the palms and is usually due to HSV infections in other body sites.
• Measles is rarely seen now that most children are vaccinated. It is the classic viral rash characterized by the onset of small red macules that expand and coalesce, starting on the head with spread downward and outward.
• Roseola is a rash that affects infants and characteristically is preceded by very high fevers that suddenly resolve as a bright red rash appears on the trunk.
• Some of the more severe viral infections may have very nonspecific and minimally symptomatic rashes such as West Nile and Zika viruses, while others have much more dramatic hemorrhagic skin findings such as Ebola virus infection and dengue fever.

Eczema or atopic dermatitis includes a wide variety of skin sensitivity in which areas of skin are dry, red, and itchy.

Bacterial

• Staphylococcus infections are extremely common and may cause many types of rashes, including folliculitis, abscesses, furuncles, cellulitis, impetigo, staphylococcal scalded skin syndrome, and surgical wound infections.
• Streptococcus infection may cause strep throat, scarlet fever, cellulitis, necrotizing fasciitis, and other skin infections.
• Pseudomonas may cause all sorts of skin problems, including green discoloration of the nails, folliculitis, hot tub folliculitis, surgical wound infections, and foot infections following a penetrating injury through tennis shoes.
• Many other types of less common bacteria cause skin rashes. These are often diagnosed by skin culture.
• Scaled patches on the palms and soles (as well as other body sites) may occur with secondary syphilis.
• Lyme disease is characterized by a slowly expanding red ring at the site of the tick bite, similar to tinea corporis (ringworm of the body), but usually without the scale.

Parasitic

Scabies is a very itchy, contagious superficial skin infestation with a microscopic mite.
Lice infestations may cause different types of itchy rashes in the affected areas like the scalp and nape of the neck or pubic area.

Causes of noninfectious rashes include:

• Drug allergies may arise from exposure to drugs containing sulfa, penicillin, antiseizure medications like phenytoin and phenobarbital, and many others.
• Contact allergic dermatitis may develop on repeat exposure to topical products like nickel, neomycin, cobalt, fragrance, adhesives, latex, rubber, and dyes. Essentially any substance may potentially induce a skin allergy.
• Eczema or atopic dermatitis includes a wide variety of skin sensitivity in which areas of skin are dry, red, and itchy.
• Hypersensitivity or allergic dermatitis may develop upon repeat exposure to poison oak and poison ivy.
• Irritant dermatitis from excessive skin dryness may develop from repeat exposure to harsh soaps and cleaning chemicals.
• Autoimmune conditions, like systemic lupus erythematosus (SLE), Hashimoto's thyroiditis, scleroderma, and other disorders in which the immune system may be overactive, often cause skin rashes. A malar or "butterfly" redness can appear after sun exposure on the cheeks. Discoid lupus is a more chronic, fixed expression of lupus of the skin that can lead to permanent scarring and skin color changes.
• Other internal diseases such as amyloidosis and sarcoidosis may cause skin symptoms and accompanying rashes.
• Lichen planus may appear as purple, itchy papules on the extremities, a large itchy plaque on the ankle, scarring hair loss, erosions in the mouth or genital area, or a combination of all of these.
• Food allergy rashes usually present as hives.

Types of itchy rashes include heat rash, hives, bug bites, scabies, eczema, and more.

Most rashes tend to be itchy, although some, especially the most serious, may be painful or burning. Rashes can be further subdivided into itchy or non-itchy.

Types of itchy rashes include

• hives and welts (urticaria),
• bug bites, including bedbugs,
• scabies (mite infestation),
• eczema (skin allergy),
• dry skin (also called "xerosis"),
• heat rash (may be irritation or superficial infection in areas of moisture, heat, friction, and occlusion), and
• some viral rashes.

Non-itchy rashes (although these may at times also be itchy) include

• rosacea and
• psoriasis.

Rashes come in many different colors, sizes, shapes, and patterns. Most rashes tend to be red because of skin inflammation. Rashes may be described as

• flat (macular),
• raised or bumpy (papular),
• raised, sheet-like (plaque),
• a mixture of flat and raised, termed "maculopapular,"
• small pus bumps (pustular),
• acneiform ("acne-like" with small or large pimples),
• small clear blisters (vesicular),
• red or pink,
• petechial (tiny pinpoint bleeding into the skin),
• silvery-white scales (psoriasis),
• annular (circular with central clearings, like in ringworm infections or Lyme disease),
• eczematous (dry, scaly, rough when early, thick, and discolored after time),
• excoriated (scratched areas). This may be superimposed on any other rash.

Noninfectious Rashes

• Contact dermatitis is a very common cause of non-infectious rash. It includes dermatitis from poison ivy, poison oak, or poison sumac, as well as other allergic skin rashes. External agents such as nickel can typically produce an inflammatory reaction over a period of time, causing itching, rash, or burning of the skin. Over the short term, this type of rash may cause superficial peeling, whereas more chronic cases cause thickened patches of skin called lichen simplex chronicus (LSC).
• Psoriasis typically looks like thickened patches of dry red skin, particularly on the knees, elbows, and nape of the neck. There are many types of psoriasis, and this type of rash may uncommonly involve the entire body and may resemble sunburn. When psoriasis involves skin folds such as the armpits or groin, it is termed "inverse psoriasis" and may show little or no scale.
• Rosacea is a type of adult acne that may cause facial flushing, small pink bumps, and redness of the cheeks and nose.
• Lupus-related skin changes are known to become exacerbated by sunlight exposure. Lupus can present as red, raised patches or a generalized rash on the nose, ears, cheeks, and base of the nail folds.
• Seborrheic dermatitis or seborrhea is a common rash that is characterized by redness and scaling of the face, ears, eyebrows, and scalp. On the scalp it is more commonly called dandruff.

Infectious Rashes

• Herpes produces groups or clusters of small watery blisters on a red base. They tend to recur periodically in the same place.
• Ringworm (tinea) leads to dry, red patches with dry skin flakes. Often there is central clearing, creating a donut pattern (annular appearance).
• Scabies may cause very itchy papules (bumps) on the scrotum or penis.

These rashes may unrelated to the pregnancy or may be unique to pregnant women. In the latter category, there are conditions including pruritic and urticarial papules and plaques of pregnancy (PUPPP), polymorphous eruption of pregnancy (PMEP), pemphigoid gestationis, and pustular psoriasis of pregnancy. Some of these can be quite severe, and their treatment, as well as the treatment of any rash in pregnancy, is complicated by concern that the treatment may have adverse fetal effects.

There are many useful laboratory and special examinations that can be helpful in the diagnosis of rash, such as

• bacterial culture to check for bacteria on the skin or in a wound;
• microscopic examination of a scraping of skin with potassium hydroxide to look for fungus;
• blood tests such as antinuclear antibody (ANA), to look for lupus, complete blood count (CBC), liver function tests (LFT) to look for rashes related to hepatitis, and thyroid function tests;
• blood test for EBV (mono) or a rapid plasma reagin (RPR) or other blood tests for syphilis may be appropriate;
• nasal culture using a cotton tip swab to check for Staphylococcus and other bacteria;
• Gram stain (special staining of a sample prior to examination under a microscope) to identify bacteria types;
• Tzanck prep to look for herpes virus under the microscope;
• skin biopsy (small skin sample or scraping sent for microscopic examination);
• patch test to determine contact allergies;
• rashes that come and go can sometimes be diagnosed by high-quality digital pictures; and
• some blood tests are less useful in diagnosis. This includes blood testing for herpesvirus and Lyme disease. The problem in both cases is that a "positive test" usually means only that the person has had or been exposed to the disease in the past and says nothing about active or current infection

Unfortunately, the skin biopsy results of viral rashes and drug rashes may be similar enough that a definite diagnosis cannot be made. Nor can a biopsy indicate which drug is the cause of a drug rash.

Sampling skin material and viewing under direct microscopy is a fast and simple way to help confirm or eliminate fungus as a cause of the rash. When a superficial fungal or yeast infection is suspected, viewing a superficial skin scraping with a potassium hydroxide prep can reveal fungal hyphae or budding cells. Prior treatment with antifungal creams may cause a false-negative test.

Likewise, suspected bacterial infection can be evaluated by a Gram stain or nasal swab culture. Viral lesions typically caused by herpes simplex can be viewed under the microscope with a Tzanck smear that will show giant, multinucleate cells.

Blood tests can be helpful as well (for example, sudden onset of severe psoriasis may be associated with an HIV infection). Anti-streptolysin O (ASO) levels can be helpful in detecting a sudden onset of guttate psoriasis associated with a recent streptococcal throat infection.

A health care provider can advise an individual regarding the suitability of these and other self-care measures for a particular condition. Some home remedies can make a rash worse by introducing additional allergens and irritants.

Eczema

• Hydrocortisone cream
• Use of soapless cleansers like Cetaphil or Dove
• Emollients such as Crisco vegetable shortening and Vaseline
• Diphenhydramine (Benadryl) for itching

Fungal Infections

• Ketoconazole shampoo to wash the affected areas
• Clotrimazole cream or terbinafine spray twice a day
• Benadryl for itching

Bacterial Infections

• Dilute vinegar soaks to affected area: Mix 4 parts water and 1 part white vinegar.
• Dilute Clorox bleach bath: ¼ cup Clorox regular bleach in one bathtub full of warm water for skin infections
• Chlorhexidine (Hibiclens) washes twice a day to affected area
• Many people are as allergic to neomycin or bacitracin as they are to poison ivy. Their use in such people complicates the clinical picture by starting a second rash on top of the first. Topical diphenhydramine (Benadryl) can have the same effect in certain people.

In general, most noninfectious rashes are usually treated symptomatically and often with cortisone creams and/or pills. Infection-associated rashes are frequently treated by addressing the underlying infection. Some treatments, such as oatmeal baths, may help control the itching of both infectious and noninfectious rashes.

Infectious Rashes

• Fungal
  • Tinea or ringworm infections of the skin, hair, and nails are treated by topical and/or oral antifungal medications like terbinafine.
  • Candida infections (yeast) are treated with topical antifungal medications like clotrimazole (Lotrimin AF, Alevazol, Desenex) and sometimes with oral antifungal drugs like fluconazole (Diflucan). Nystatin will not treat ringworm, nor will griseofulvin treat yeast.
  • Atypical fungal infections, including cryptococcosis, aspergillosis, and histoplasmosis, are generally treated with an oral or intravenous course of special antifungal medications.
• Viral
  • Herpes infections are usually treated with oral or intravenous antiviral medications, including acyclovir (Zovirax), famciclovir (Famvir), valacyclovir (Valtrex), ganciclovir (Cytovene), and cidofovir (Vistide). Depending on the severity of the individual infection and factors relating to the patient's immune system, specific antiviral treatment may not be required or more aggressive treatment may be recommended.
  • Vaccination is an effective prevention measure to help ward off infections with the herpes zoster virus, which causes chickenpox and shingles.
  • There is no currently vaccine available for herpes simplex.
  • HIV infections are treated with a special combination of antiviral medications designed specifically for this virus.
  • Most other viral infections are self-limited and often may clear even without any treatment.
• Bacterial
  • Staphylococcus infections are typically treated with dicloxacillin and cephalosporin antibiotics. Topical treatment may include mupirocin cream or ointment (Bactroban).
  • A resistant form of Staphylococcus called methicillin-resistant Staphylococcus aureus (MRSA) is treated based upon specific antibiotic testing. Common antibiotics for treatment of MRSA infections include doxycycline (Vibramycin, Oracea, Adoxa, Atridox, Acticlate, Doryx), sulfamethoxazole-trimethoprimFloxin
  • Streptococcus infections are typically treated with oral or injectable antibiotics, including penicillin and erythromycin (Eryc, Ery-Tab, E.E.S, EryPed, PCE).
  • Pseudomonas infections are treated with oral or intravenous antibiotics, including ciprofloxacin (Cipro, Cipro XR, Proquin XR) or ofloxacin (Floxin).

Noninfectious Rashes

• Treatment of a rash due to a drug allergy includes stopping the responsible drug. Sometimes, a short course of oral steroids may be required in severe cases to help clear the rash. A rash may persist for days or weeks after discontinuing the offending drug.
• Therapy for contact allergic dermatitis includes withdrawal of the offending topical agent and use of topical steroid creams like clobetasol (Cormax, Embeline, Temovate, Olux, Clobex) or hydrocortisone cream.
• Treatment for eczema or atopic dermatitis includes a wide variety of skin-care measures, including lubrication and topical steroids, as well as oral antihistamines like diphenhydramine (Benadryl) for itching. Nonsedating antihistamines, while effective for hives, do not work as well for common eczema.
• Hypersensitivity or allergic dermatitis from poison oak and poison ivy is treated by washing off the plant's oily resin from the skin, clothing, and objects like golf clubs or shoes and applying steroid creams to the rash two to three times a day. Severe cases may require oral steroids like prednisone. The rash may last for another two to three weeks after a single exposure and will usually have a delay in onset of two to four days.
• Irritant dermatitis is treated by skin lubrication, avoidance of harsh soaps and chemicals, use of petrolatum (Vaseline), and topical steroids like hydrocortisone.
• Autoimmune conditions such as lupus (SLE) are treated by addressing the overactive immune reaction. Often oral and topical steroids are used to help control symptoms. Additional medications include hydroxychloroquine or immune-suppressing medications such as azathioprine (Imuran, Azasan) or mycophenolate mofetil (CellCept).

Individuals should consult with their health care provider before starting any medications. The following are examples of effective treatments for specific types of rashes.

Eczema

• Steroid creams like clobetasol, triamcinolone, and hydrocortisone
• Oral corticosteroids may be used for flares, and long-term immunosuppressive medications may be required in long-term sufferers.

Fungal Infections

• Clotrimazole
• Terbinafine
• Ketoconazole

Bacterial Infections

• Staphylococcus infections: cephalexin
• Pseudomonas infection: ciprofloxacin
• MRSA infection: doxycycline, trimethoprim-sulfamethoxazole

Dermatologists (skin specialists) are best equipped to diagnose and treat most rashes, especially those that require biopsy or special tests. Unfortunately, there may be quite a delay in obtaining a dermatologist consult in some areas. For that reason, most primary-care physicians (family physicians, internists, and pediatricians), as well as those who work in urgent care and emergency departments, will be the first to see a patient's rash and, in many cases, can make accurate diagnoses and advise effective treatment. Allergists treat many rashes also, especially those related to hives. Occasionally, an infectious-disease specialist may be involved in the treatment of rashes caused by severe or unusual infections. Medical or surgical oncologists may have a role when a skin rash is due directly or indirectly to an underlying cancer.

The outlook for rash depends on the underlying cause. The prognosis of clearing a superficial fungal infection is very good while a patient with psoriasis or eczema may not clear completely despite aggressive therapy. Most rashes are short-lived and easily resolve. There are some chronic rashes that are not curable, such as psoriasis. Medical monitoring is often necessary to watch the progression of more resistant or recurrent rashes. Any persistent rashes or rashes that are refractory to appropriate treatment may warrant a skin biopsy to rule out cancer.

Risk factors and preventive measures to avoid a problem depend upon the type of rash.

Eczema

Avoid offending or irritating agents like harsh soaps and cleansers if one has contact dermatitis. Patch testing with special allergens should be done if there is suspicion for topical allergies. Keep the affected area moist with cream/ointment or emollients.

Viral Infection

Avoid infected people, especially with active chickenpox. Some viral infections can cause harm in pregnancy to the unborn fetus. Bodily fluids such as blood, respiratory droplets, and saliva also should be avoided to prevent infection.

Bacterial Infection

Hand washing and proper hygiene are very important in prevention. Avoid shaving with dirty razors. Use special precautions in public facilities, including gyms, showers, and pools to help prevent infections. Do not keep razors in the shower; the warmth and humidity encourages bacterial growth.