What is contact dermatitis?

Contact dermatitis, much like the name suggests is inflammation (dermatitis) in the skin caused by direct contact with a particular substance. Unlike in AD the skin has no in-built weakness and the inflammation occurs solely due to exposure to the trigger.

There are two main types of contact dermatitis: allergic and irritant. Both subtypes experience the same symptoms but have different mechanisms.

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What is actually happening in your skin?

In irritant contact dermatitis the outer layer of skin is directly damaged by contact with the substance leading to skin inflammation. This means that anyone can develop this if exposed to a sufficient damaging substance. Factors which determine the likelihood of developing the condition include the concentration of the irritant, duration of exposure and frequency of exposure. An individuals skin type can impact the likelihood of developing the condition with thin, dry and previously damaged skin weakening the defence to irritants. 

In allergic contact dermatitis the substance does not directly damage the skin but triggers an allergic reaction leading to inflammation. This process is more complicated and unpredictable. In simple terms a substance (antigen) which is not usually harmful penetrates through the first layer of your skin and is taken up by immune cells leading to a process called sensitisation. On repeated exposure to this substance the body perceives this as a threat triggering a substance specific inflammatory reaction in the skin. This results in a series of chemicals being released by these immune cells which create symptoms such as hives, redness and weeping of the skin etc. 

Common features of contact dermatitis

Contact dermatitis is characterised by an itchy red rash upon coming into contact with the substance usually effecting the hands. Typically an irritant reaction occurs within a few hours after exposure while allergic reactions can take 1-2 days to develop. Other symptoms that may occur include: 

Burning / Blistering / Hives / Scaling / Pain 

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How is contact dermatitis treated?

The most important thing is to identify the trigger and avoid further exposure. For irritants this is usually fairly easy to establish due to symptoms developing soon after exposure. For allergic contact however this can be much more difficult, patch testing is the gold standard test for determining the exact cause. 

If you do come into contact with the substance washing the traces off thoroughly with warm water can be helpful.

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Treatments for dermatitis include:

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Moisturisers -  which help boost the skin’s defences by adding moisture to damaged skin and preventing further water loss.

Topical steroids - which suppress the inflammatory reaction in the skin. These are available in varying strengths based on the severity of inflammation and sensitivity of the skin to the medication.

In severe cases oral steroids and calcineurin inhibitors  may be beneficial for short periods of time.

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