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What is a rash?

A rash is an inflammatory reaction of the skin. Rashes can be caused by a wide variety of mild to serious diseases, disorders and conditions. Rashes can affect a small area of the skin or the full body and occur in all age groups and populations.

Rashes vary greatly in appearance, extent and severity, depending on the underlying cause. Rashes can be red, white, purple or silver in color, and raised, bumpy or flat in texture. They can appear as dots or spots or occur in a large, continuous area. Rashes can also include scaling or flaking off of skin cells.

Because of the range of possible causes of a rash, a correct diagnosis of the underlying disease, disorder or condtion  is very important. Contact your health care provider for a physicial exam.

A rash of purple spots can indicate a serious, potentially life-threatening condition, such as meningitis or allergic purpura. A rash that is associated with allergies combined with shortness of breath, wheezing, or swelling of the face, mouth or throat is also a symptom of a serious, potentially life-threatening allergic reaction called anaphylaxis. Seek immediate medical care (call 911) if you, or someone you are with, have any of these symptoms.


What other symptoms might occur with a rash?

A rash may be accompanied by other symptoms, depending on the underlying disease, disorder or condition. Other symptoms may affect the digestive tract, respiratory system, nervous system, reproductive system, cardiovascular system, immune system, or integumentary system (skin and associated tissues).

Skin symptoms that may occur along with a rash

A rash may occur with other symptoms affecting the skin including:

  • Blistering

  • Burning

  • Inflammation

  • Irritation

  • Itching

  • Redness

  • Scaling

  • Swelling

Other symptoms that may occur along with a rash

A rash may occur with other symptoms related to other body systems including:

Serious symptoms that might indicate a life-threatening condition

In some cases, a rash may occur with other symptoms that might indicate a serious or life-threatening condition, such as anaphylaxis, that should be immediately evaluated in an emergency setting. Symptoms that may indicate a serious or life-threatening condition include:


What causes rashes?

Rashes can be caused by a wide variety of diseases and conditions, such as infection, inflammation, allergic reaction, parasite and insect bites, and autoimmune processes.

Infectious causes of rashes

A rash may be caused by an infection including:

    Allergic causes of rashes

    A rash may be caused by an allergic reaction including:

    Autoimmune causes of rashes

    A rash may be caused by an autoimmune response including:

    Parasites, insects and arachnids that cause rashes

    A rash may be caused by parasites, insects or arachnids including:

    Other causes of rashes

    A rash may also be caused by problems in body systems other than the skin including:

    Life-threatening causes of rashes

    In some cases, a rash may accompany a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

    • Allergic purpura

    • Anaphylaxis

    • Meningitis

    • Severe allergic reaction

    Questions for diagnosing the cause of a rash

    To diagnose the underlying cause of a rash, your doctor or licensed health care practitioner will ask you several questions related to your symptoms. You can best help your health care practitioner in diagnosing the underlying cause of your rash by providing complete answers to these questions:

    • Describe the rash. Where is it? What does it look like?

    • Did the rash develop suddenly or slowly? Is it constant or intermittent?

    • Does the rash occur with any particular activity, such as eating?

    • What other symptoms are you having?

    • Have you been in recent contact with any unusual or new substances or environments, such as poison ivy or new medications or food?

    • Have you experienced any recent insect or animal bites?

    • Provide your full medical history, including all medical conditions, surgeries and treatments, family history, and a complete list of the medications and dietary supplements that you take.

    What are the potential complications of a rash?  

    In some cases, a rash can lead to complications, especially if the itching is severe and leads to breakdown of the skin. Complications include:

    • Bacterial or fungal infection of the skin

    • Cellulitis (an infection of the skin and surrounding tissues caused by a growing bacterial or fungal infection)

    • Open sores and lesions

    • Permanent change in skin texture or scarring

    • Permanent skin discoloration

    Was this helpful?
    Medical Reviewer: William C. Lloyd III, MD, FACS
    Last Review Date: 2018 Dec 19
    1. Allergic Diseases Resource Center. World Allergy Association. http://www.worldallergy.org/adrc/
    2. Rashes. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003220.htm
    3. Skin Rashes and Other Changes. American Academy of Family Physicians. http://familydoctor.org/online/famdocen/home/tools/symptom/545.html
    4. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012. 
    5. Bope ET, Kellerman RD (Eds.) Conn’s Current Therapy. Philadelphia: Saunders, 2013.
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