- What is Contact Dermatitis?
- Risk Factors
- Clinical Examination
- How is it Diagnosed
What is Contact Dermatitis?
Dermatitis means inflammation of the skin caused by something touching the skin. Contact dermatitis is a condition referring inflammation caused by direct contact with an irritating or allergy provoking substance. The two main types of contact dermatitis include:
- Irritant contact dermatitis
- Allergic contact dermatitisIrritant dermatitis is the most common type of contact dermatitis, which involves damage to the skin resulting from contact with acids, alkaline substances such as washing detergents, soaps, solvents and other chemicals.The second most common type of contact dermatitis is allergic contact dermatitis, which is caused by exposure to a material to which the person has become hypersensitive or allergic. The skin becomes inflammed and disease can range from mild (producing irritation and redness), to severe, involving open sores and intense redness. This depends on the amount and type of irritant contacted, the skin sensitivity of the patient and the body part affected. In cases of contact dermatitis from work, the most common area involved is the hands.
The most common type of dermatitis is irritant contact dermatitis, which accounts for about 80% of all cases of contact dermatitis. In Australia, occupational irritant contact dermatitis contributes to time taken off work – the incidence of confirmed cases of irritant contact dermatitis is 20.5 per 100,000 workers. This means that out of 100,000 workers, about 20-21 people suffer from occupational contact dermatitis, which may necessitate taking time off work and change of occupation.
If you have had or suffer from allergic conditions such as eczema, hay fever or asthma, or there is a strong family history of these conditons, you may have more sensitive skin and be more likely to develop contact dermatitis.
Factors that may aggravate irritant dermatitis include:
- Water, especially frequent hand washing and prolonged contact with water.
- All types of soaps, detergents, shampoos and other cleaning agents.
- Solvents such as turpentine, kerosene, fuel, thinners
- Oils and cooling fluids
- Hot temperatures and sweating
- Dusts in the environmentAllergic contact dermatitis may involve a reaction to a substance that you are exposed to or use repeatedly. Although there may be no initial reaction, repeated use (for example, repeated contact with metals in the back of earring posts and the metal backs of watches) can cause sensitization of the skin with time, and reaction to the product.Causes of allergic contact dermatitis include:
- Common metals such as nickel and cobalt. Allergy is common in women who wear jewellery, from the backing of watches and jean studs and buckles.
- Chemicals used in the manufacture and preservative of rubber products, such as thiurams, mercaptobenzothiazoles and carbamates.
- Hairdressing allergens such as hair dyes (paraphenylene diamine or PPD) bleach (ammonium persulfate and hydrogen peroxide).
- Chromate, which is present in cement and leather.
- Substances applied to the skin such as preservatives in products such as creams, gels, lotions, shampoos; antiseptics in hand creams; fragrances (often in toiletries) deodorants.
Most cases of irritant contact dermatitis develop over time, with frequent and repeated exposure to skin irritants such as water, soaps and detergents. Allergic contact dermatitis is caused by an allergy to something which comes in contact with the skin and causes a delayed reaction. It is called a delayed reaction because the rash may not appear for some time after contact with the allergic substance, ranging from hours to days.
The rash seen in allergic contact dermatitis is often similar to the rash of irritant contact dermatitis. Most contact dermatitis resolves spontaneously in about four to six weeks if further exposure is prevented. However, we have to identify the agents that are causing the dermatitis to be able to achieve long term control of disease.
When you visit the doctor, he or she may ask the following questions, as necessary, to try and identify the most likely diagnosis and cause for your symptoms.
- What is your occupation?
- Have you had repeated exposure to any allergens / irritants or do you notice any initiating or aggravating factors relating to episodes of contact dermatitis? (In acute allergic contact dermatitis, the lesions usually appear within 24-96 hours of exposure to the allergen).
- Where is the contact dermatitis predominantly located? (Parts of the body which come in contact with particular substances may help identify the cause).
- Are there any associated symptoms such as itch, redness, warmth, tenderness or signs of infection (pus, skin redness, fever)?
- Is there a history of previous contact dermatitis or a similar presentation?
- Have there been any new medications / cosmetic or chemical applications that have been applied to the skin?
Most cases of contact dermatitis appear in a similar fashion, regardless of the mechanism or cause of inflammation. The different responses can be categorized into acute, subacute, and chronic phases, depending on the time course taken for the disease to develop.
When your doctor examines you, he or she may look for the following features.
- Acute contact dermatitis usually appears as a rash with small, clear, fluid filled pockets that develop on red and swollen skin. As the lesions break down, the skin can begin to weep fluid.
- Subacute contact dermatitis is characterized by less swelling and formation of papules.
- Chronic contact dermatitis presents with minimal swelling. Features such as scaling, fissuring / cracking of the skin and thickening of the surface layers of the skin may be present..
How is it Diagnosed
The doctor will usually be able to make a diagnosis of contact dermatitis based on what is present clinically and no specific tests are necessary. The rash will usually clear up if contact with the allergic / irritating substance is avoided. In some cases of contact dermatitis, you may visit a skin specialist called a dermatologist, to have patch testing performed.
Patch testing is the special technique used to diagnose causes of allergic dermatitis.
Small amounts of diluted chemicals are placed on discs, about the size of a 5c coin. The discs are placed on a strip of tape called a patch, there are about 10 discs per patch. Several patches are then stuck onto your back and left there for 48 hours. The doctor will give you specific instructions such as keeping your back dry and not scratching the tape. After 48 hours, the tapes are removed and your back is observed for any allergic reactions. You usually return for a further reading after another 2-3 days.
Most cases of contact dermatitis are easily treated and will resolve with time if we avoid the substance that is causing the allergic or irritant reaction. In a few cases where the cause is unidentified, the outlook in the long term is not as favourable. Occasionally, contact with an allergy provoking substance can precipitate a reaction involving the immune system which results in a type of shock called anaphylactic shock.
The most important step in successfully managing contact dermatitis is to recognise how you are in contact with the allergic substance, so that you can avoid it. General measures to help relieve some of the symptoms and discomfort associated with contact dermatitis include:
- Emollient creams or ointments help soften the skin and moisturisers add moisture. These products are used to improve dryness and scaling of the skin and irritant contact dermatitis.
- Topical steroids are very effective and safe medications when used correctly. These work by reducing inflammation of the skin. Topical steroids should be applied once or twice daily to the areas of skin affected by disease.
- Topical or oral antibiotics may be used to treat secondary infection.
- Short courses of oral steroids may be used for severe cases of dermatitis. Corticosteroids have anti-inflammatory effects and modify the body’s immune response to various stimuli.In all cases of contact dermatitis, antihistamines (such as Phenergan)may be used as adjuncts to relieve associated itch. If you have been unresponsive to the above measures, further treatment in the form of photochemotherapy and drugs affecting the immune system such as azathioprine, cyclosporin, and tacrolimus may be another option to consider. Your local health professional will be able to provide you with more information about these treatments.
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