What are Skin Rashes?

Healthy skin provides a barrier between the inside of the body and the outside environment. A rash means some change has affected the skin.

Rashes are generally caused by skin irritation, which can have many causes. A rash is generally a minor problem that may go away with home treatment. In some cases a rash does not go away or the skin may become so irritated that medical care is needed.

In adults and older children, rashes are often caused by contact with a substance that irritates the skin (contact dermatitis). The rash usually starts within 48 hours after contact with the irritating substance. Contact dermatitis may cause mild redness of the skin or a rash of small red bumps. A more severe reaction may cause swelling, redness, and larger blisters. The location of the rash may give you a clue about the cause.

Contact dermatitis does not always occur the first time you are in contact with the irritating substance. After you have had a reaction to the substance, a rash can occur in response to even very small amounts of the substance. Contact dermatitis is not serious, but it is often very itchy. Common causes of contact dermatitis include:

Poisonous plants, such as poison ivy, oak, or sumac

Soaps, detergents, shampoos, perfumes, cosmetics, or lotions

Jewelry or fabrics

New tools, toys, appliances, or other objects

Latex. Allergy to natural rubber latex affects people who are exposed to rubber products on a regular basis, especially health care workers, rubber industry workers, and people who have had multiple surgeries. Latex allergies can cause a severe reaction.

Rashes may occur with viral infections, such as herpes zoster; fungal infections, such as a yeast infection; bacterial infections; and sexually transmitted infections. Rashes may also occur as a symptom of a more serious disease, such as liver disease, kidney disease, or some types of cancer.

Rashes may also appear after exposure to an insect or a parasite, such as the scabies mite. You may develop a rash when you travel to a rural area or go hiking or camping in the woods.

A rash may be a sign of a chronic skin problem, such as acne, eczema, psoriasis, or seborrheic dermatitis. Other causes of rash include dry, cold weather; extremely hot weather; and emotional stress. Emotions such as frustration or embarrassment may lead to an itchy rash.

Some medicines can cause a rash as a side effect. A very rare and serious type of generalized red rash called toxic epidermal necrolysis (TEN) may occur after using sulfa drugs. TEN can cause the skin to peel away, leaving large areas of tissue that weep or ooze fluid like a severe burn. TEN may occur after the use of some medicines. If this type of rash occurs, you need to see a doctor.
The need for medical treatment often depends on what other symptoms are present. A rash that occurs with other symptoms, such as shortness of breath or fever, may mean another problem, such as a serious allergic reaction or infection.

Symptoms and Signs

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

bug bites, including bedbugs

scabies (mite infestation)

eczema (skin allergy)

some viral rashes

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


rosacea

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 (papular)

a mixture of the above two, termed maculopapular

small pus bumps (pustular)

small clear blisters (vesicular)

red or pink

petechial (tiny pinpoint bleeding into the skin)

silvery white scales (psoriasis)

annular (circular with central clearing, 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 noninfectious rash. It includes dermatitis as from poison ivy, oak, or 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 water 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.

Causes

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

The following are causes of infectious rashes.

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.

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. 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 virus, while others have much more dramatic hemorrhagic skin findings such as Ebola virus infection.

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 causes 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 scalp and nape of the neck or pubic area.

The following are causes of noninfectious rashes.

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 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.

Diagnosis

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.

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.

Western Medicine Rash Treatment

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 and sometimes with oral antifungal drugs like fluconazole. 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.

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.

A resistant form of Staphylococcus called methicillin-resistant Staphylococcus aureus (MRSA) is treated based upon specific antibiotic testing.

Streptococcus infections are typically treated with oral or injectable antibiotics, including penicillin and erythromycin.

Pseudomonas infections are treated with oral or intravenous antibiotics.

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 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 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.

Home Remedies

A health-care provider can advise an individual regarding the suitability of these and other self-care measures for a particular condition.

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: quarter cup regular bleach in one bathtub full of warm water for skin infections

Chlorhexidine 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.

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.

Prognosis

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 resolved. 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.

Adopted from emedicine.com