What causes underarm rash?

Underarm rash may have many possible causes, including allergens (agents that cause allergies), infections, autoimmune disorders, or other causes such as stress.

Allergic or inflammatory causes of underarm rash

Underarm rash may be caused by contact dermatitis. Common triggers include:

  • Cosmetics, dyes or detergents
  • Industrial chemicals, such as those found in elastic, latex and rubber
  • Metallic substances (various metals, copper, wire)
  • Poison ivy or oak

Other allergic or inflammatory causes of underarm rash include:

  • Eczema (skin disorder causing scaly or blistering rashes that may be caused by allergy)
  • Folliculitis (inflammation of the hair follicles that may occur after shaving)
  • Food allergies (allergic reactions to certain foods)
  • Ingrown hairs after shaving
  • Insect bite allergy such as a bee sting

Infectious causes of underarm rash

Underarm rash can also be caused by infections including:

  • Chickenpox or shingles
  • Eczema (skin disorder causing scaly or blistering rashes that may be caused by infection)
  • Impetigo
  • Lyme disease (inflammatory bacterial disease caused by ticks)
  • Measles, mumps, rubella, roseola, or scarlet fever
  • Meningitis (infection or inflammation of the sac around the brain and spinal cord)
  • Pityriasis rosea (rash resembling the shape of a pine tree)
  • Ringworm
  • Rocky Mountain spotted fever
  • Strep throat (bacterial throat infection)

Autoimmune causes of underarm rash

Underarm rash can also be caused by autoimmune disorders including:

  • Kawasaki disease (rare, serious pediatric disorder characterized by inflammation of blood vessels, high fever, rash, and mucous membrane changes)
  • Psoriasis
  • Rheumatoid arthritis (chronic autoimmune disease characterized by joint inflammation)
  • Systemic lupus erythematosus (disorder in which the body attacks its own healthy cells and tissues)

Other causes of underarm rash

Underarm rash can be caused by other factors such as:

  • Acne
  • Extreme cold or heat
  • Medications

Serious or life-threatening causes of underarm rash

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

  • Allergic purpura
  • Anaphylaxis (life-threatening allergic reaction)

Questions for diagnosing the cause of underarm rash

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your rash including:

  • When did the rash begin?
  • Are you taking any medications?
  • Do you have any known allergies?
  • Did the rash start in one location and spread to another?
  • Does the rash cause any itching or scaling?
  • Do you feel otherwise healthy?
  • Have you tried any new products recently, such as soaps, perfumes, sprays or deodorants?
  • Have you spent a lot of time outdoors lately?

What are the potential complications of underarm rash?

Because underarm rash may be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. For example, infectious diseases, such as mumps or measles, can lead to rare but serious complications, including miscarriage, hearing loss, and serious brain infections, such as encephalitis or meningitis. Lyme disease can progress to cognitive and functional impairments.

Once the underlying cause of your rash is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Arthritis
  • Cognitive difficulties
  • Encephalitis (inflammation and swelling of the brain due to a viral infection or other causes)
  • Meningitis (infection or inflammation of the sac around the brain and spinal cord)
  • Miscarriage or stillbirth
  • Paralysis
  • Permanent hearing loss
  • Secondary infections, which may develop from scratching and related skin trauma


  1. Skin rashes and other changes. FamilyDoctor.org. http://familydoctor.org/online/famdocen/home/tools/symptom/545.html.
  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.

What is underarm rash?

Rash is a symptom that causes the affected area of skin to turn red and blotchy and to swell. A rash may cause spots that are bumpy, scaly, flaky, or filled with pus. Rashes can vary in location, pattern and extent and may occur in any area of the body. A rash under your arm can have a variety of causes, and it may indicate something occurring around the underarm itself or suggest a systemic (b... Read more about underarm rashintroduction


What other symptoms might occur with underarm rash?

Underarm rash may be accompanied by other symptoms, depending on the underlying disease, disorder or condition. Certain conditions that cause underarm rash may also involve other body systems.

Related localized symptoms that may occur along with underarm rash

Underarm rash may be accompanied by other localized symptoms including:

Medical Reviewer: Cynthia Haines, MD Last Annual Review Date: Aug 11, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Skin, Hair and Nails

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