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Mar 18, 2020
4 min read

Contact dermatitis: allergic and irritant eczema

Contact dermatitis belongs to the eczema family of skin disorders. There are two types of contact dermatitis: irritant contact dermatitis and allergic contact dermatitis. Irritant contact dermatitis happens when your skin comes into direct contact with chemicals, moisture, heat, or excessive friction. Allergic contact dermatitis is a delayed immune system reaction to an allergen. The best treatment for contact dermatitis is avoidance.

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

Contact dermatitis, sometimes called allergic eczema, occurs when your skin comes into contact with something that you are allergic to (an allergen) or that irritates your skin (an irritant), which causes a rash on the skin. According to the American Academy of Dermatology (AAD), nearly everyone experiences contact dermatitis at some point in their lives (AAD, n.d.).

There are two main types of contact dermatitis: irritant contact dermatitis and allergic contact dermatitis (NEA, n.d.). Contact dermatitis tends to be more common in women than in men; it also causes approximately 10% of all work-related diseases. People at risk include hairdressers, beauticians, nursing staff, metalworkers, or anyone in an occupation with frequent exposure to certain chemicals.

Contact dermatitis is part of the family of skin disorders known as eczema. However, it is not the same as atopic dermatitis (sometimes called eczema). Atopic dermatitis is a skin condition that causes dry, itchy, scaly patches to appear. It is mainly caused by genetics, environment, and immune system sensitivities.

Contact dermatitis, on the other hand, is in response to certain irritants or allergens, and these triggers can be different for different people. By avoiding exposure to the irritant or allergen, you can prevent contact dermatitis. Sometimes the appearance of contact dermatitis looks like atopic dermatitis. Consulting with a dermatologist (skin specialist) may help distinguish between the two.

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What causes contact dermatitis?

As mentioned, there are two types of contact dermatitis: irritant contact dermatitis and allergic contact dermatitis. Irritant contact dermatitis happens rapidly after your skin touches a chemical, leading to a rash or other signs of skin irritation. Moisture, heat, or excessive friction can also cause this type of contact dermatitis. Irritant contact dermatitis is the most common type of contact dermatitis (NEA, n.d.). Examples of irritant contact dermatitis include:

  • Diaper rash
  • Dry, cracked skin from too much hand washing
  • Chapped, irritated lips from lip licking
  • Irritation from direct contact with harsh chemicals like bleach, hair dyes, or battery acid

Allergic contact dermatitis is the other primary type of contact dermatitis (NEA, n.d.) and is a specific type of allergic reaction called type IV hypersensitivity reaction. In this type of allergic response, the first time you are exposed to the allergen (the thing you are allergic to), you don’t have a reaction. Instead, your cells send a piece of the allergen to your immune system so that it can recognize it the next time you are exposed to it (this is called sensitization).

The next time your body encounters that allergen, your immune system recognizes it and mounts an allergic reaction with skin rash, irritation, etc. This delayed response is why you can develop a contact dermatitis reaction to a cosmetic or soap product that you have used before. Also, this reaction can take 48–96 hours to manifest, unlike irritant contact dermatitis that can occur quickly after exposure. Examples of allergic contact dermatitis include:

  • Poison ivy or poison oak
  • Latex allergy
  • Cosmetic or soap allergies
  • Nickel allergy (reaction from jewelry)
  • Fragrances
  • Antibacterial ointments

Signs and symptoms

The most common symptoms include:

  • Red skin or rash
  • Itching
  • Dry skin
  • Inflammation
  • Burning around the affected area
  • Blisters that “weep” or crust over

The symptoms of contact dermatitis can range from a minor annoyance or a severe reaction. Because it is a type IV hypersensitivity reaction, contact dermatitis symptoms typically take several hours up to 10 days to develop after exposure to the allergen or irritant (ACAAI, n.d.). Contact dermatitis is not contagious; you cannot get a rash from someone who has contact dermatitis.

How is contact dermatitis diagnosed?

Contact dermatitis is usually limited to the areas of exposure, especially in the case of irritant contact dermatitis. Often with a good history and examination, your healthcare provider can diagnose contact dermatitis. However, if the rash does not go away after a few weeks or has other concerning features, additional tests may be warranted.

Patch testing is sometimes used to diagnose cases of suspected allergic contact dermatitis. During this test, patches that have suspected chemical allergens in them are left on your skin for 48 hours. Your provider will check on those areas after removing the patches and then again several days later to see if you develop any skin reactions. If so, then you are allergic to that particular chemical.

Treatment of contact dermatitis

The best treatment for contact dermatitis is to remove the offending substance and avoid exposure to it in the future (if possible). For example, if the nickel in your jewelry is causing a rash, then only wear nickel-free jewelry. In specific cases, there may be additional treatments you can follow. If you have dry, chapped hands or lips from frequent hand-washing or lip-smacking, frequently moisturizing may improve your symptoms.

Alternatively, you can soothe the itch of a poison ivy rash with calamine lotion or oat baths; however, this won’t treat the rash itself. Many parents are familiar with diaper rash creams that help their little ones feel better. If the rash does not improve on its own, your healthcare provider may recommend steroid cream treatments or oral antihistamines.

References

  1. American Academy of Dermatology (AAD) – Contact dermatitis (n.d.). Retrieved 20 April 2020, from https://www.aad.org/public/diseases/eczema/types/contact-dermatitis
  2. American College of Allergy, Asthma, and Immunology (ACAAI) – Contact Dermatitis (n.d.) Retrieved 20 April 2020, from https://acaai.org/allergies/types/skin-allergies/contact-dermatitis
  3. Institute for Quality and Efficiency in Health Care (IQWiG) – Allergic contact dermatitis: Overview. 2017 Jul 13. Retrieved 20 April 2020, from https://www.ncbi.nlm.nih.gov/books/NBK447113/
  4. National Eczema Association (NEA) – What is contact dermatitis and how is it treated? (n.d.). Retrieved 20 April 2020, from https://nationaleczema.org/eczema/types-of-eczema/contact-dermatitis/