About contact dermatitis

Contact dermatitis, or contact eczema (‘dermatitis’ and ‘eczema’ can be used interchangeably) is the name given to types of eczema that occur as a result of contact with irritants or allergens in the environment. Contact dermatitis affects 9% of the UK population and is the most common type of work-related skin disease.

What is contact dermatitis?

Contact dermatitis can be broadly divided into two types: irritant contact dermatitis (ICD), where eczema develops as a result of contact with substances that directly damage or irritate the skin; and allergic contact dermatitis (ACD), which develops when an individual becomes sensitised or allergic to something in the environment. However, there is overlap between the two and it is possible to have both at the same time.

What is irritant contact dermatitis?

Irritant contact dermatitis is a reaction to frequent contact with everyday things that irritate the skin, such as soap, detergents, oils, hair cosmetics, bleach, household cleaning products, cold wind, and raw food. 

Common sites for irritant contact dermatitis are the hands and face, but the condition can affect other parts of the body. A person who had atopic eczema as a child is at an increased risk of developing irritant contact dermatitis.

Symptoms of irritant contact dermatitis range from mild dryness and skin redness to the appearance of skin burns. It can be painful, red, fluid-filled and ulcerated.

Occupations at greatest risk for developing irritant contact dermatitis include: chefs, hairdressers, metal workers, nurses, cleaners and construction workers.

What is allergic contact dermatitis?

Allergic contact dermatitis is much less common than irritant contact dermatitis. It is caused by an individual developing a specific allergy to a chemical. For an allergy to develop, repeated exposure to the chemical is required over a period of time, usually months or years.

Once this has happened, the body’s defence mechanisms learn to recognise the chemical and the individual develops a reaction when the chemical contacts the skin again. The allergy is ‘remembered’ by the body for many years. In medical terms the body has become ‘sensitised’ to a chemical.

The reaction can be immediate or delayed depending on the type of allergen in question. Most frequently seen on the hands, allergic contact dermatitis can cause the skin to become dry, red, split, cracked, weeping, fluid-filled and intensely itchy, sore, painful and stinging. The severity will depend upon the allergen and the length of time it is in contact with the skin.

The most common contact dermatitis allergens in Europe are: fragrance, thiomersal (antiseptic), cobalt (cement), nickel, paraphenylenediamine (hair dye, henna, temporary tattoos) and formaldehyde (chemical preservative).

If allergic contact dermatitis is thought to be a possibility, then you need to be referred to a dermatologist, who may recommend patch testing.

Patch testing

Patch testing is a valuable way of identifying triggers for contact dermatitis, but the process can be intense. Claire Moulds provides a practical guide to help you get the most out of the experience. This article was published in Exchange 184, June 2022.

Patch testing is an important investigative procedure that can be used to find out whether your eczema is caused by an allergy to a substance that comes into contact with your skin. The experience can be challenging – especially if you’re being tested for a lot of different potential allergens, or if you have multiple reactions.

What happens?

You’ll need to attend hospital three times over a period of five days:

Appointment 1: Each potential allergen is applied to your back in a small container, held in place by hypoallergenic tape, and the location marked on your skin with marker pen.

Appointment 2 (48 hours later): The tape and allergens are removed and any reactions noted. If a sunlight-induced contact allergy is suspected, part of the area being tested may be exposed to ultraviolet light.

Appointment 3 (another 48 hours later): The skin is examined again for reactions and the results discussed with you.

You must not allow the areas being tested to get wet, until the patch-testing process is complete.

Planning ahead

You’ll be asked to bring in your own creams, toiletries and cosmetics, including the packaging, so the team has a list of ingredients to work with. Not all packaging includes a complete list of ingredients (for example, laundry products), so you may need to go onto the manufacturers’ websites in advance and print out full lists. Think of absolutely everything that comes into contact with your skin – not just the obvious ones. For example, what’s in your period products?

As well as booking time off work for the appointments, you will definitely experience some level of discomfort while wearing the containers and tape and may find sleep elusive, so plan your week accordingly. Self-care tips might include working from home, scaling back social commitments or organising additional childcare – especially if you have young children who require a lot of physical interaction.

Allow extra time for your appointment as you may need to be at the hospital for longer than the two-to-three hours advised.

If it’s your child who is being tested, alert the school in advance, book time off for all three appointments, organise exemption from PE – to avoid excess sweating, swimming, showering – and make sure they have someone at school who is aware of the test and who they can flag any problems with. To avoid getting the testing area wet while maintaining your appearance, you might want to book in a wash and blow dry with your hairdresser.

Positive reactions during the patch-testing process can lead to a flare up of your eczema, so make sure you have all your emollient and medications on hand.

Getting ready to go

Before you leave, have a thorough shower and wash your hair, as you won’t be able to do either for five days. Don’t apply cream or ointment to areas that may be used for testing. If you are petite, or are being tested for lot of potential allergens, the team might apply allergens to other parts of your body, as well your back, so keep your arms, stomach and legs clear just in case.

Don’t wear your best clothes or underwear, or any pale garments, as the allergens and the marker ink may permanently stain them. If your child is going to school afterwards, arrange for them to wear a T-shirt under their uniform, to protect from staining.

Protecting the test

Once the team have applied the allergens, do whatever you can to keep them in place so that you get the clearest results possible:

  • Before you leave the clinic, ask for a roll of hypoallergenic tape to take home with you so you can re-tape any patches that become loose.
  • During the five-day period, minimise movement. However hard it is, staying still will help the patches remain in contact with the skin, making for a more accurate end result.
  • Wear something in bed to protect the patches. Some people prefer a loose T-shirt, while others a tight vest. If the garment doesn’t cover all the patches or marker pen, be aware your bedding may become stained – especially if you get hot and sweaty.
  • If you’re prone to moving around a lot in bed, try using pillows to help secure your body in one position, to help stop the patches coming loose in the night.
  • Avoid the sun: make sure you don’t expose any area being tested to direct sunlight.

Your final appointment

At your third visit, tell the healthcare professional about any patches that are itchy or painful, as these symptoms are invisible to the naked eye. Ask them to send you a list of all the things you’ve reacted to, if they don’t do this automatically, and for advice on how to manage future reactions if you’re unexpectedly exposed.

After the testing

Once the patch-testing process is complete, you’re free to go home and shower. The allergens will easily wash off your skin, but the marker-pen ink will continue to fade over the coming week.

  • Resist the urge to speed up the process by bathing excessively or by aggressively scrubbing your skin.
  • Be aware that you might experience a delayed allergic reaction. If you think you have experienced a late reaction, take photos of the affected skin and contact the patch-testing clinic.
  • Reactions generated by the patch-testing process – especially the more severe ones – may take time to fully heal. Follow the advice given by the clinic team and apply any medication that they prescribe.

From the results, use your list of allergens to carry out a thorough audit of your home – including your car, garage and shed. Ideally, assess your working environment too, by finding out what cleaning products they use and cross-check their ingredients with your list.

Managing your feelings

Patch testing can be empowering, as it helps you identify allergens you need to avoid to protect your skin. But if you don’t have a positive reaction, it can be very frustrating. Especially if you have waited a long time for the test, it may feel as if your hopes of revealing the cause of your skin problems are dashed. However, even a negative result can be helpful as it excludes allergy as the cause of your eczema. This knowledge puts you in a stronger position, enabling you to refocus your efforts on other avenues.

For more information on contact dermatitis, treatments and patch testing, please see our Contact Dermatitis booklet.