What Causes a Rash?
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.
- 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.
- 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.
- 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.
- 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'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.
Medically Reviewed by a Doctor on 7/27/2016
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