Contact Dermatitis (Contact Eczema)

ICD is not linked to allergy, rather it is a skin response to physical and toxic effects of external substances, including over-washing, harsh detergents, industrial cleaners or solvents, cement and acids. 

The European Society of Contact dermatology have compiled a list of the top 10 most common contact allergens in Europe. In 2024, this is the most recent top ten:

1. Nickel 

2. Fragrances mix

3. Cobalt – metal allots

4. Methylchloroisothiazolinone (MCI/MI) –preservatives

5. PPD (p-phenylenediamine): hair dyes and temporary tattoos

6. Formaldehyde – preserving fluid

7. Myroxylon pereirae resin – Balsam of Peru  - cosmetics, sunscreens, foods

8. Thiomersal – make up, soap, topical antibiotics

9. Potassioum Dichromate –leather, inks and dental implants

10. Chromate – cement, building materials

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.

A person who had atopic eczema as a child has an increased risk of developing irritant contact dermatitis. Occupations with a greater risk include: chefs, hairdressers, metal workers, nurses, cleaners and construction workers. 

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 you suspect you have allergic contact dermatitis, then you need to be referred to a dermatologist, who may recommend patch testing.