I have heard a lot about different allergy tests and am confused. My local supermarket offers tests of this kind, and a friend has also suggested an ELISA test. Can you give me any more information about these types of test and allergy tests in general?

‘Allergy tests’ mean different things to different people, and you will hear a lot of conflicting information about their use. Broadly speaking, there are two types of allergy test applicable to skin disease:

• patch tests
• skin-prick tests (this type of testing can also be carried out on blood samples with an ELISA test, but both of these techniques are testing the same thing).

Patch tests look for evidence of contact eczema (also called dermatitis), such as is seen in allergy to nickel, chromate, rubber, dyes, glues or perfumes. This is a delayed allergy that sometimes develops after repeated exposure to a substance.

Contact eczema is uncommon in children, perhaps because they have not had enough exposure to these allergens, so patch tests are not needed (or indeed helpful) in uncomplicated atopic eczema in childhood.

Patch tests are complicated to do and interpret (they are carried out only by specialist dermatologists) but are useful in investigating certain types of eczema – such as isolated hand eczema, especially in people with certain jobs, for example hairdressers, builders and nurses.

Skin-prick tests (or ELISA tests) look for an immediate type of allergy (type 1 allergy). There are hundreds of allergens that can be used in these tests, but the common ones are pollens (grass and tree), dog fur, cat fur, house dust mite, egg, milk, fish and nuts. They can be useful in detecting relevant allergens in asthma, food intolerance and hay fever.

They do not, however, provide much, if any, useful information in atopic eczema, and most experts in childhood eczema now realise this. The majority of children with eczema have multiple positive results to the skin-prick test, and these are difficult to interpret in any useful way.

Children’s skin seems hyperreactive to many substances. Although some doctors still do these tests, we believe that it is unjustified to inflict 15 pin-pricks or a blood test on a young child with atopic eczema if it is not going to provide any practical information in helping to manage the eczema.

These tests do not help in deciding whether a certain food might make eczema worse and, if they are wrongly interpreted, can cause problems if nutritional foods are unnecessarily excluded.

I sent a piece of my hair away for testing and it came back with a whole list of foods that I am allergic to. My GP doesn’t believe the result and says I should see an immunologist. Can’t I just stop eating all those foods?

There is a great problem with the sort of testing you have had done. Often, there is very little science behind the test and the results, and we feel that the people doing the tests have a financial interest in the test being positive.

Immunologists work much more with properly researched and what we call ‘evidence-based’ tests so can give more accurate results. If you tried to avoid the ‘whole list of foods’, your health would probably suffer greatly so it is not safe just to stop eating them.

Any dietary modification should be carried out with advice, and perhaps supervision, from a dietitian. Immunologists may need to play a bigger role in managing cases like yours in the future, especially when tests for ‘intolerance’ as opposed to true allergy are established and properly validated. To date, however, there are very few immunologists in the NHS, and waiting lists are long.

My doctor has refused to do allergy tests on my daughter – can I insist that these be done? It sounds as though you and your doctor have a problem. Words like ‘refuse’ and ‘insist’ are very strong as you need to be able to discuss the investigation and treatment of your daughter’s eczema in a calm way.

If you read through the answers given above about allergy testing, it might help you to understand why such tests are not likely to change the way in which your daughter is treated. This is a very important concept, and doctors are often the worst offenders in carrying out tests unnecessarily.

With eczema, it is very difficult to justify the pain inflicted on your daughter by having the tests done, and in today’s tightly budgeted NHS we have to look at the cost of tests as well as treatment, and be able to justify the expense.

I have a leg ulcer but also seem to have developed eczema on my leg. Is this caused by the ulcer? Having an ulcer does mean that the skin on your leg is weak and prone to damage so you are more likely to develop irritation and even allergies to the various treatments used for your ulcer.

It is not therefore a direct effect but is a consequence of having the ulcer. The bandaging used to treat the ulcer occludes the skin and increases the likelihood of a reaction to creams or dressings under the bandages. You might need to have patch tests to check for allergies to substances being used to treat your ulcer.

My eczema doesn’t seem to behave as it should! I keep getting flares around my eyes and eyelids, and my GP can’t explain why. I always use the same creams, which sometimes work and sometimes don’t. Should I see a consultant?

This is a common presentation of any allergic contact eczema. Unusual patterns like this should always suggest the need for allergy testing. The skin around the eyes and on the eyelids is very sensitive, and one common cause of allergy is actually nail varnish.

We are sure you are not applying nail varnish anywhere near your eyes, but you might be surprised how often you touch this area, and if you are wearing nail varnish this can cause a reaction. It could also be a reaction to any make-up you might use intermittently around the eyes, and you could also have developed an allergy to one of your treatments.

I recently had to go to hospital for patch-testing and found out I was allergic to nickel. I try to make sure I don’t come into contact with it, but I still seem to get eczema. Is nickel eczema just from contact with it?

You have probably been given a list of metals that contain nickel, but it also occurs in many foods, which could be a reason for your eczema continuing. You could also have several different triggers for your eczema, not just nickel.

Cheap jewellery is not the only source of direct contact with nickel as it is unfortunately present in many common items made of, or containing, metal:

• clothes fastenings such as jeans studs, hooks and zips
• other personal objects – cigarette lighters, wristwatches, key rings, keys, parts of spectacle frames and pens
• household items such as drawer and cupboard handles, kitchen utensils, toasters, etc.
• silver coins.

The list could almost be endless so only a few examples are given here. The nickel content of some foods comes from natural sources or from the way in which they are prepared. This is usually only a problem if you have a severe reaction to nickel, which often shows up as a blistering eczema (pompholyx) on the hands.

Avoid canned foods, and use aluminium or stainless steel utensils when cooking. A dietitian could give you a list of foods to avoid, which will include asparagus, oysters, herrings (other fish are OK), mushrooms, onions, tomatoes and rhubarb.

Is it worth having tests for food intolerance? I have recently read about this testing and about claims that most people get better after testing, although nothing has been published. Is it worth doing?

These tests are being developed but, at the time of writing, have not been fully evaluated or validated. This process is very important if the tests are to be used to change treatments or dietary habits. Tests need to be accurate and repeatable – this means that they should give the same result no matter how many times you are tested before having any treatment so that changes in the results can be believed.

Could I sometimes be allergic to dairy products and sometimes not? I notice that my skin sometimes seems to get worse when I drink milk?

One possible explanation may be that the lining of the gut can become inflamed when eczema is severe, and larger proteins than normal can get through. These larger proteins may trigger an immune response and cause further exacerbations, but once the eczema has settled, the gut returns to normal and the larger proteins are kept out.

My asthma flared up recently, and my doctor told me to stop taking aspirin or Nurofen. Could these also have been causing my eczema?

Some people with atopic diseases such as eczema, asthma and hay fever are sensitive to the effects of ‘salicylates’. These are naturally occurring substances very similar to aspirin, which was derived originally from willow bark.

Nurofen and other ‘non-steroidal antiinflammatory drugs’ have a similar action to aspirin and can share some of its potential reactions. This appears to be much more of a problem with asthma than eczema. Salicylates tend to give an urticaria (hives) rather than eczema, but they could be a factor for you.

I work in a sawmill and get eczema on my hands. This is put down to wear and tear, but recently I got eczema on my face, which I think is also worse at work. Could it be something in the air?

You could have a combination of a physical contact irritant eczema from the wear and tear, and an allergic form from natural resins in the wood or agents used to treat the wood. If the ventilation is poor and the atmosphere you work in is heavy with dust, you could well get an allergic reaction on your face. Talk to your GP about a referral for patch-testing.

My parents have always recommended massaging mustard oil into the arms and legs of our children to help with strong bone growth. I have a 3-year-old daughter with eczema and am worried that this might make it worse. What should I do?

We have come across the practice of using mustard oil on the skin in families from Africa and the Indian subcontinent. There isn’t any scientific evidence that this practice helps with bone growth, but many people are strong believers in it. It is important to try to respect cultural practices as they may be helpful, or at least not harmful, to eczema.

For example, many West Indian and Indian parents use olive oil or aloe vera cream as a moisturiser, and these seem to be beneficial. Some Nigerian families use hibiscus flower water on the skin; although we are not sure that this helps, it certainly does not seem to make things worse.

Mustard oil, however, is very irritant to the broken skin of eczema and will nearly always make it worse. Because of this, we strongly advise you not to use it. A balanced diet with plenty of calcium and exercise will ensure good bone growth. You will have to explain to your parents politely, but firmly, that mustard oil would make their grand-daughter’s eczema worse and that she is growing into a healthy girl without it.

All my children have suffered with bad cradle cap and nappy rash. Why is this, and why did they all get better after a few months?

It sounds as though all your children had seborrhoeic eczema. In a mild form, this is almost universal in babies. It is probably caused by a transfer of hormones (androgens) from mother to baby just before birth. These hormones act to stimulate the grease glands (sebaceous glands) of the skin, making them overactive.

They are usually inactive in children until puberty. This hormonal stimulation causes the greasy scaling so typical of this type of eczema. The scalp and nappy area are commonly affected – hence the usual presentation with cradle cap and nappy rash.

As babies do not make these hormones themselves, and because the transferred hormones are soon broken down and inactivated, the problem of seborrhoeic eczema resolves completely on its own in a few months.

I suffer with eczema on my hands, which I think is made worse by work, although I work in an office and don’t handle any chemicals. Could there be another explanation?

Your work environment might be a problem as the low-humidity from air-conditioning can dry out anybody’s skin, and this will be a bigger problem for you. It will show up as redness and scaling. Repeated friction from handling papers or other materials can also be a problem, leading to a physical eczema that will differ in looking less red, but dry and thickened.

I have just come back from holiday with the most awful eczema. My doctor says it is photo-dermatitis and might be due to a new sunscreen. Will I ever be able to go on holiday again?

Yes, you will. A type of allergic contact eczema whose cause involves natural or artificial ultraviolet light is quite rare but may be on the increase. Sunscreens are the most commonly reported culprits (photo-allergens), but they are always used in the sun!

Other common photo-allergens are fragrances, topical non-steroidal anti-inflammatory drugs and some antibacterial creams. You might need to be referred to hospital for a special form of patch-testing that uses ultraviolet light to mimic the conditions in which you reacted – this is called photo-patch-testing. This should allow the dermatologist to tell you what sunscreens you can safely use.

I first started having eczema around my fingernails, which might have been due to the false nails I wore. I then got it in my hair – have I transferred it to my scalp from my fingers when I wash my hair?

Eczema is not a contagious disease so you will not have transferred it to your scalp. As you have developed eczema around your fingernails from an allergy to the acrylics in false nails, you do have a risk of developing eczema elsewhere.

Once you have an allergy to something, any part of your skin can react in the same way, so if you washed your hair with the false nails on, this might have been enough contact to start the eczema. There may, however, have been a different trigger for your scalp eczema, such as a different shampoo or hair treatment.

One of the residents in the nursing home where I work had scabies. I caught it and had treatment, but my doctor says I now have eczema. Does scabies cause eczema?

It is very common to have a rash that looks just like eczema after scabies (an infestation with little mites that burrow into the skin) as you will have developed an allergy to the dead mites and their waste matter.

Standard eczema treatments should settle it down over a few weeks, but it will leave your skin in a vulnerable state for the next few months so soaps and other products that might not have bothered you before could cause a problem. Take good care of your skin and it should all settle down and not trouble you again.

I think something in my garden makes my eczema worse. Any clues you could give me would be welcome as I don’t want to give up gardening.

There are many things in the garden that can cause skin problems, some of which are quite dramatic, with acute blistering rashes from a combination of plant juices and the sun. It sounds as though you already have eczema that gets worse when you garden, and this could be due to several factors.

The very act of using your hands outdoors, with rubbing, hard work and the extra washing required, can cause problems in terms of physical irritants.

Some plants are associated with eczema; these include chrysanthemums, which tend to give a thickened, dry eczema on exposed parts, and tulip bulbs, which classically give rise to a fingertip eczema. The pollen in the air near chrysanthemums can cause the reaction so you don’t even have to be in direct contact.