Contact Dermatitis: Causes and Treatment

You have had an itchy patch for weeks now. How can you tell if it’s contact dermatitis and what is the best form of treatment for this allergic reaction?

What is Contact Dermatitis?

Contact dermatitis, also known as contact allergy, is an allergic skin reaction that typically shows up as an itchy rash that sometimes develops into blisters and swelling. 

Symptoms of Contact Dermatitis

The most common manifestation of contact dermatitis is an itchy rash that develops over a few days, after your skin has come into contact with a particular allergen or substance. You will likely start to feel an itch in the affected area, before developing red swells and water bubbles on your skin. Although usually confined to the area of contact, the rash may sometimes spread to other parts of the body.

Occasionally, the rash that develops from contact dermatitis may be more chronic, manifesting as an itchy patch that does not heal for weeks or even months. This usually occurs when there is frequent contact with the substance, such as a watch strap. This rash is known as contact dermatitis.

Figure 1. Allergic contact dermatitis to plaster.

Figure 2. Allergic reaction to flavine, spreading to other parts of the body.

Causes of Contact Dermatitis

A substance that causes contact allergy is called a contact allergen. 

Some common contact allergens are:
Metals such as the nickel in watch straps and chrome in cement
Skincare products that contain fragrances or lanolin
Medication that include components such as flavine or neomycin

Diagnosing Contact Dermatitis

A skin test known as a patch test can be used to confirm a contact allergy. 

The test involves applying a small amount of the suspected contact allergen, diluted in a non-irritant concentration, onto the skin and sealing it with hypoallergenic tape. Several suspected allergens can be tested simultaneously. They are left on the skin for 48 hours and read at 48 and 96 hours. A positive reaction to the test indicates that you are allergic to the test substances. This is a very safe procedure. 

A patch test is important as it will help to ascertain the cause of your allergy.

Treatment Methods for Contact Dermatitis

In many cases, avoiding the cause of your allergy is a form of treatment. There is often no cure for a contact allergy and future contact with the substance will likely result in contact dermatitis again. It is advisable for patients to carry a card with them to remind themselves and their doctors of their contact allergy.

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