Rashes: Common Causes, Symptoms, & Treatments

By Nancy Youssef, MD
Medically reviewed
May 1, 2020

The human skin is our bodies’ largest organ. As the protective barrier between our environment and internal organs, it reacts to irritants we come into contact with and conditions that are affecting us internally.

When individuals have a skin rash, it means they have a patch of either itchy, swollen, irritated, or painful skin somewhere on their body. Some rashes can develop into raw areas of skin, and others can lead to blisters or small bumps. A rash can cover large parts of the body, or stay confined to a single spot. It can develop within minutes or over the course of several days. Some rashes go away on their own, and some are longer lasting and require long-term treatment.

What causes rashes? There are many possible causes for each type of rash. Some rashes are due to outside elements and others are due to internal health issues. Some rashes can be a symptom of a wide variety of medical conditions. For example, contact dermatitis, a common, often itchy rash, can appear if your skin touches a chemical irritant or certain plants (poison ivy rash and poison oak rash are both considered forms of contact dermatitis). Another example is a short lived heat rash which appears on people who have issues sweating or when the skin is exposed to high temperatures. Another example is a stress rash, which can develop on people who are under significant emotional strain. Rashes can also be a symptom of more significant underlying health issues, including fungal, bacterial, and viral infections.

So how can you tell if a rash is serious? In this article, I’ll dive into common skin rash types, explain their causes, and discuss the treatment options that you can use to soothe and heal your skin.

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What Is a Rash?

A rash is an area of skin that is irritated or inflamed. Rashes are changes to the skin and often but not always, itchy, painful, red, and swollen. They can appear as welts, blotches, small bumps, or large blisters, and affect multiple patches of skin or a single area. Rashes can develop quickly or over time, and indicate anything from an allergic reaction to an underlying infection.

Although they can be upsetting to patients, most rashes are not contagious or dangerous to others. Many rashes will go away on their own or can be successfully treated with soothing creams, lotions, and other topical treatments found over-the-counter (OTC) or made right at home.

If you have developed a mild rash and you are not experiencing any other symptoms, it is reasonable to wait a few days to see if your rash will go away on its own. If the rash has persisted for a few days or spreads, become painful or infected, or you’ve developed a fever, your rash may indicate a medical condition that requires treatment. Talk to your doctor or dermatologist and make an appointment to be seen.

Types of Rash

Rashes can be caused by all kinds of things, including chemical irritants, allergies, heat, stress, insects, autoimmune conditions, medications, and viral, fungal, and bacterial infections.

Rashes that aren’t contagious

Common rashes that aren’t considered dangerous to others—either because they can’t be spread, or aren’t caused by an infection that can be spread—include:

  • Contact dermatitis: an allergic reaction rash that appears where your skin has made contact with a chemical or natural irritant like poison ivy, poison oak, poison sumac, or an insect bite.
  • Atopic dermatitis (eczema): a very common, chronic skin condition and autoimmune response that often appears in childhood among patients with a genetic predisposition to the disease.
  • Seborrheic dermatitis: an itchy, flakey rash, sometimes called “dandruff” or “cradle cap,” that commonly affects both infants and adults 30-90, and appear on patients’ scalp and/or head. This condition can also be associated with atopic dermatitis.
  • Stasis dermatitis: a long-term condition that most often affects patients over 50. This is often located in both legs to become inflamed, swollen, itchy, and to develop ulcers. This is often due to pressure due to not moving for long periods of time and having fluid collect on the lower legs. Often patients have conditions like high blood pressure or congestive heart failure or other venous insufficiency.
  • Heat rash: is fan adverse skin reaction to high temperatures or humid weather that occurs when a patient’s blocked pores trap sweat underneath the skin.
  • Hives: are often itchy welts or bumps that can appear in reaction to different irritants, including allergens, sunlight, exercise, insect bites, tight clothing, and stress.
  • Psoriasis: a skin disorder in which skin cells multiply faster than usual, creating areas of red, bumpy patches covered in white silvery scales, most often on the scalp, elbows, and knees.
  • Malar rash (lupus rash): a symptom of lupus that appears as a purple or red rash on patients’ faces in a butterfly shape over the nasal bridge and cheeks.
  • Drug eruptions: any adverse skin reaction that patients develop as a result of new or changed medication.
  • Rash during pregnancy: there are numerous different rashes that develop as a result of the hormonal changes that women undergo during pregnancy.

Contagious rashes

Common rashes that are considered contagious or infections are the following:

  • Molluscum contagiosum: a viral infection most commonly found in children and presents as red, firm but painless bumps on the skin and often flesh colored with a dimple like center.
  • Cellulitis: a bacterial infection that causes painful, swollen skin that feels hot and tender to the touch. It can release pus that can lead to becoming an abscess.
  • Impetigo: a highly contagious skin infection caused by strains of strep or staph bacteria that affect infants and children, and appears as an orange, honey-like rash and commonly found on the face.
  • Herpes rash: an infection that is spread through contact or prior reactivation of the chicken pox. A herpes rash is a vesicular rash that presents as a collection of small blisters. If it’s a genital herpes rash, it is due to sexually transmitted disease. If it’s a cold sore herpes infection, this can be transmitted through kissing or touching an object that has the herpes virus and then touching your lips. This kind of herpes is found in over 90% of the population. Another form of herpes is shingles, in which the chicken pox infection is reactivated—often due to illness or stress. This rash is in a linear pattern on the body and doesn’t cross the midline of the body. All herpes rashes are painful and have a burning sensation.
  • Ringworm: a fungal infection spread by skin-to-skin contact that causes itchy, circular rashes with clear skin in the middle. This occurs often when the skin is damp or wet. To prevent fungal infections keep the skin dry.
  • Rubeola (measles rash): a rash caused by a very infectious airborne disease that appears as reddish-brown and covers patients from head to toe and there are spots inside their mouths. Other presenting symptoms are a cough and fever.
  • Scabies rash: small fluid-filled blisters, pink pimples, or gray streaks caused by contagious mites that burrow into the top layer of human skin.
  • Meningococcal septicemia (sepsis): a contagious and very serious bacterial infection of the blood that first presents tiny pink, brown, or purple pin-prick marks, bruise-like marks, or blotchy skin. This also can appear with a fever.
  • Syphilis rash: a sexually-transmitted rash that presents differently, depending on how long someone has been infected. In its first stage, it may look like a single or group of firm, red, painless sores around the mouth or groin, while in later stages, it can present as a rash anywhere on your body, including the palms of your hands and bottoms of your feet.
  • Lyme disease rash: a rash that occurs when someone is infected with Lyme from an infected deer tick, appearing first as a small red bump at the site of the bite, and then expanding outwards over the next 2-30 days to create a bullseye pattern.

Common Causes of Rash

Rashes are caused by a wide variety of health conditions, medications, and ailments. Common causes of rash include:

  • Irritants
  • Allergens
  • Heat
  • Stress
  • Bacterial infections
  • Viral infections
  • Fungal infections
  • Medications, particularly penicillins, sulfa drugs, anti-seizure drugs, allopurinol, and cephalosporins
  • Autoimmune conditions
  • Parasites

Symptoms of Common Rashes

Irritated skin can manifest in a wide variety of shapes, sizes, and colors. Rashes may range from red to purple and brown, and some present as lighter skin when appearing on darker skin tones. They can be raised or swollen, itchy, flakey, painful, or none of those things. They can have irregular edges or appear circular, involve bumps and pimples, plaques, tags, ulcers, or pin-prick patterns and ooze, weep, or remain dry to the touch.

Many common, mild rashes are not dangerous and will go away on their own or with light over-the-counter topical treatments. However, your rash might indicate an underlying condition that requires medical treatment. Talk to your doctor or dermatologist to schedule an appointment if you experience a rash that persists for more than a few days, worsens over time, or also experience symptoms that include:

  • Fever
  • Significant pain
  • A rash that rapidly spreads or extends all over your body
  • Bruise-like lesions
  • Blisters
  • Skin infections

How are Rashes Diagnosed?

When diagnosing a specific rash, a doctor or dermatologist will take a look at the irritated or inflamed portion of the patient’s skin and note any other symptoms you might be experiencing. They may ask about your environment, including questions that might shed light on any chemical or natural irritants you might have recently come into contact with. They may ask about your allergy history, or ask you to take an allergy test to determine if you’ve become newly sensitive to certain foods, plants, or animals. They may note your family history to determine whether you have a genetic predisposition to certain rashes and ask about any current or former medications to rule out any adverse drug reactions.

In the case of a suspected fungal, bacterial or viral infection, a doctor may ask to take a blood sample or a culture of the rash to examine in a laboratory.

Treatment Options for Rashes

Individual treatment plans depend on your age, symptoms, and health. They can include rest and fluids, over-the-counter and prescription topical treatments, ointments and creams, antihistamine medications, and at-home treatments. If a bacterial infection is present, your doctor may prescribe a course of oral antibiotics.

If the rash is related to a parasitic or fungal infection, you may be asked to wash your clothes, bed linens, or other household items in hot water. If the rash is the result of an interaction with an allergen or irritant, your doctor may ask you to avoid any contact with that food, plant, or substance.

At-home remedies can help patients soothe mild to moderate rashes and help heal their skin more quickly. Not all at-home treatments will work for every rash so make sure you can identify what’s causing your rash before trying one of these at-home remedies. Effective treatments can include:

  • Warm compresses: This type of at-home treatment is specifically helpful for abscesses or boils. Warm compresses can help boils begin to remove pus which will reduce its size and pain. This may help relieve symptoms until you are seen by a physician for antibiotics or outpatient surgical care.
  • Oatmeal bath: If you have the chicken pox or an allergy-like rash, this may be an effective at-home remedy. Soaking in a bath with colloidal oatmeal is a traditional and effective way to treat itchy skin conditions, like allergic reactions and chicken pox.
  • Over-the-counter antihistamine creams and medications: These medications can be useful for allergy reactions of the skin like contact dermatitis which is caused by an allergen touching the skin and hives occurs in the area. This also can be helpful for insect bites like mosquito bites that can cause itching and swelling.
  • Emollients: Emollients, or moisturizers, are often first line treatments for atopic dermatitis. These are products like Vaseline, Aquaphor, and Eucerin cream which are moisturizing and soothe skin like atopic dermatitis or eczema if used often.
  • Anti-fungal creams: Ringworm and other fungal infections can occur from contact and are exacerbated by dark, damp, and wet environments of the skin. The areas affected are often the armpits, under the breasts, under the belly, or in the genital areas. Using over-the-counter creams that are for fungal like infections, like terbinafine (Lamisil), can help reduce the infection.
  • Over-the-counter antiviral medications: Docosanol (Abreva) and other cold sore lip balms may help if used early to reduce the size and pain of a cold sore.
  • Stress reduction: Many skin reactions can occur due to stress. When you notice this happening, try to reduce the stress in your life by sleeping well and taking care of your health overall.

For many skin reactions, avoiding certain products with alcohol or fragrances can help reduce skin irritation and allergy-like reactions. Make sure to always wear sunscreen when going outside—even when it doesn’t feel super sunny.

When to See a Doctor

Although many rashes are mild and go away on their own, some indicate more serious health conditions that require medical treatment. If you have a rash that persists more than a few days, spreads quickly or gets worse over time, is painful, infected, blisters, or covers a significant portion of your body, it’s important to speak to your doctor or dermatologist to schedule an appointment.

If you develop a skin rash and a fever of 100.5° F (38° C) or higher, you may have a serious medical condition that requires immediate medical treatment. Talk to a doctor or visit the nearest emergency room to be seen as quickly as possible.

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How K Health Can Help

It’s important to identify and understand what’s causing your rash so you know how to treat it. Did you know you can get affordable primary care with the K Health app? Download K to check your symptoms, explore conditions and treatments, and if needed text with a doctor in minutes for possible treatment. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Nancy Youssef, MD

Dr. Youssef is a board certified family medicine physician who completed her residency at at Advocate Christ Medical Center and later obtained her teaching in family medicine fellowship at Tufts/Cambridge Health Alliance Family Medicine. She graduated from the University of Illinois. Aside from her work at K Health, Dr. Youssef is currently working in urgent care and primary care specializing in Women's Health.

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