I Have This Rash … The Most Common Infectious Rashes We Treat

By Sarosh Khan, MD

Common infectious rashes including shingles, Lyme disease, measles, scabies, ringworm & more

Rashes can be painful, itchy, unsightly and sometimes mysterious. A rash occurs when the skin becomes inflamed, red and can have bumps or sores although not always. Just about everyone will get a rash at some point in their lives.

We often get this question: “I have this rash, doctor. Can you tell me what it is and cure it?”

While infectious diseases, including infectious rashes, are our focus, we can also help patients who have a noninfectious rash that is persistent, severe and/or difficult to diagnose. Rashes are not just annoying, they can lead to serious medical conditions and can be a symptom of undiagnosed systemic infections such as HIV (human immunodeficiency virus).

When to seek help for a rash

If a rash is persistent, severe or if you’re unsure of the cause, it’s best to consult a healthcare provider, including our ID Care specialists. We can provide proper diagnosis and a treatment plan for any rash.

Types of rashes: noninfectious and infectious rashes

Noninfectious rashes

Noninfectious rashes are usually caused by irritation, immune system issues or allergies. These include:

• Eczema.
• Psoriasis.
• Contact dermatitis such as poison ivy.
• Allergic reactions to food, insect bites and medications.
• Others such as heat rash and seborrheic dermatitis.

These rashes are not contagious and usually respond to avoiding the triggers that cause them, using moisturizers, and applying over-the-counter or prescription medications as needed.

Infectious rashes such as viral rashes

An infectious rash is not exactly the same thing as a skin infection, but it can be a symptom of a skin infection.

Related Reading: Skin Infections (cold sores, MRSA, cellulitis, impetigo & necrotizing fasciitis)

The term infectious rashes refers to those caused by a skin infection. Infectious rashes are very common and can be triggered by:

• Bacterial infections that can be common and treatable or life-threatening.
• Viral infections, also known as exanthems.
• Parasitic infections.
• Fungal infections.

Following is information on the most common infectious rashes we see and treat at ID Care.

Shingles (Herpes zoster) from chickenpox

The varicella-zoster virus first causes chickenpox, characterized by itchy, fluid-filled blisters all over the body. The virus can then lie dormant for years after recovery from chickenpox and later reactivate as shingles, also known as Herpes zoster.

Shingles is a viral infection that causes a painful, blistering rash, usually in a single stripe on one side of the body. Symptoms can persist for weeks, months or even years. While there is no cure, we treat shingles with medications to attack the virus and lessen pain. Shingles can be prevented with a Shingrix vaccine, which is recommended for certain population groups.

Related Reading: Shingles

Measles rash

Measles (rubeola) is a highly contagious virus. The first symptoms mimic the flu, then after a few days Koplik’s spots appear in the mouth followed by the measles rash.

The measles rash appears as large blotches that merge together and develops 3-4 days after the first symptoms of measles. The rash generally begins around the face and spreads to the legs and arms.

We can’t cure the measles rash but we can lessen some of its symptoms and the risk of it spreading. We strongly advise children to get the measles vaccine (MMR vaccine).

Related Reading: Measles, symptoms and treatments

Lyme disease rash (erythema migrans)

Lyme disease develops from tick bites. The Lyme disease rash, also called erythema migrans, is a bacterial infectious rash.

It most commonly appears as a uniformly red, round or oval patch that slowly expands around the site of a tick bite. It often looks like a “bull’s eye,” usually larger than 2 inches, and may expand more over several days or weeks. In some cases secondary erythema migrans lesions can also appear far from the bite site and may have a variety of appearances.

The rash develops in about 70% of people with Lyme disease, according to the Centers for Disease Control and Prevention. It is not typically painful, hot or itchy. Antibiotics are most frequently used to treat the Lyme disease rash.

Related Reading: Lyme disease

Secondary syphilis rash

The secondary syphilis rash is a bacterial infectious rash. Syphilis is a sexually transmitted infection that can develop in four stages. If treatment doesn’t occur in the first stage, it can become secondary syphilis.

At this point the patient can experience the secondary syphilis rash, which is rough and bumpy. This is usually a non-itchy rash that can cover the entire body and is often located on the soles of the feet and the palms of the hands.

The secondary syphilis rash can clear without treatment. However, treatment is still crucial to eliminate the infection and prevent damage to organs and the nervous system.

Related Reading: Syphilis

Candidiasis rash (cutaneous candidiasis)

A candidiasis rash, also called cutaneous candidiasis, is a fungal, infectious rash caused by an overgrowth of Candida yeast. The candidiasis rash is a yeast infection that most often occurs in warm, moist areas of the body such as the underarm, groin, under a woman’s breasts and near the buttocks. It can be a cause of diaper rash in children.

The candidiasis rash can cause burning and itching, which can be intense. Its appearance can vary depending on where on the body it occurs. The rash often appears in moist, red patches. Pimple-like bumps can form around these patches.

Good hygiene can help prevent the candidiasis rash. Over-the-counter antifungal creams and powders can help cure it. Prescription antifungal medications may be necessary.

Tinea (ringworm)

Tinea, more commonly known as ringworm, is not caused by a worm but by the fungi dermatophytes. Tinea corporis is ringworm on the body that shows up as itchy, circular, scaly patches with raised edges.

Antifungal medications in creams, pills, powders and sprays can treat forms of tinea. Different types of tinea relate to where it occurs on the body.

Tinea pedis (athlete’s foot)

This occurs on the feet and between the toes. It is itchy and can cause burning, scaling and blisters.

Tinea cruris (jock itch)

Tinea cruris is commonly known as jock itch, occurring in the groin and inner thighs. It can be red and itchy. It is notorious for being hard to cure for some people.

Tinea capitis

Tinea capitis occurs on the scalp as small, scaly patches that itch. It is most common in children and often requires prescription medication.

Tinea unguium

This infectious rash affects the nails, which become thick, discolored and brittle. 

Scabies

Scabies is a parasitic infectious rash caused by the Sarcoptes scabiei mite. These mites dig down under the skin where they live and lay eggs, particularly in skin webs and folds. The scabies rash is a reaction to the mites.

This is a very contagious condition, as mites spread from person to person with direct contact or contact via shared clothing or bedding. In the United States it is more likely to occur where people live closely together, such as dorms and nursing homes.

A scabies rash is very itchy, even more so at night. Sores can sometimes become infected due to scratching. The rash can look like pimples or hives and vary in color depending on the person’s skin tone. The mites’ burrow tracks may appear as thin, raised lines on the skin. The rash spreads slowly, sometimes for as long as months.

Treatment involves applying antiparasitic creams, ointments and lotions. We may prescribe the antiparasitic pill ivermectin to treat scabies.

Drug-related rashes such as hives

Drug-related rashes, or drug eruptions, are skin reactions that occur in response to a medication. These rashes can range from mild, itchy bumps to severe, widespread conditions like Stevens Johnson syndrome, which is a serious condition usually requiring hospitalization. Hives is a common drug-related rash.

They can come on in hours or weeks after starting a medication. The type of drug-related rash depends on the medication. These are generally related to a reaction to a medication or a side effect from taking a medication.

As there are so many medications, diagnosing the cause of drug related rashes can be complicated. Once the medication is identified and discontinued, the rash will usually clear. Corticosteroids and antihistamines can be part of treatment.

Other infectious rashes

We see patients with a wide range of infectious disease–associated rashes. In addition to the more common ones cited above, following is a list of others:

• Rubella.

• Roseola (HHV-6).

• Hand-foot-mouth disease (Coxsackie virus).

• Parvovirus B19 (erythema infectiosum).

• Scarlet fever (Group A strep).

• Meningococcemia.

• Rocky Mountain spotted fever.

• Cryptococcosis / histoplasmosis / coccidioidomycosis (disseminated).

• EBV + amoxicillin rash.

• Herpes simplex virus (HSV)

• HIV acute retroviral syndrome.