Contact dermatitis is a rash caused by your skin reacting to a substance it has come into contact with. You may need patch testing to identify the causative substance. A steroid cream or ointment will usually clear the rash. However, the long-term treatment is to avoid contact with the causative substance.
What is dermatitis?
Dermatitis means inflammation of the skin. Dermatitis is also called eczema. It causes red, itchy skin which may also blister. There are several types of dermatitis. However, dermatitis is generally grouped into two main types:
- Dermatitis caused by a problem from within the body. For example, atopic eczema (atopic dermatitis) is a common condition which tends to run in families. If you have atopic eczema you are born with a tendency for your skin to become inflamed. Various parts of the skin tend to flare up with inflammation from time to time. See separate leaflet called 'Atopic Eczema' for more details.
- Dermatitis caused by a substance from outside the body. This typically causes patches of inflammation on areas of skin which have come into contact with the substance. This is called contact dermatitis. If you avoid the offending substance, the skin inflammation should go away.
The rest of this leaflet is only about contact dermatitis.
Types of contact dermatitis
There are two types of contact dermatitis - irritant and allergic.
Irritant contact dermatitis
This is caused by direct contact with a substance which irritates the skin. This is common and causes about 8 in 10 cases of contact dermatitis. It most commonly affects the hands. Irritant substances are those that can cause inflammation in almost everyone if they are in contact for long enough, often enough and in strong enough concentration. For example:
- Detergents (washing-up liquid, soaps, bleach, etc). People who do a lot of cleaning are prone to irritant contact dermatitis.
- Solvents (such as petrol), oils and other chemicals used in various places of work.
- Acids and alkalis, including cement.
- Powders, dust and soil.
- Certain plants (for example, ranunculus, anemone, clematis, hellebore, mustards).
You can develop irritant contact dermatitis quickly from a single exposure to a strong irritant. For example, from contact with a strong chemical in a work situation. However, you may also develop irritant contact dermatitis because of repeated exposures to weaker irritants. For example, from a detergent that you use when washing up dishes regularly.
There is often a vicious circle. A patch of skin may become sore after being in contact with an irritating substance. This causes some skin damage. Once damaged, the skin is more easily affected by irritants. So, further contact, even with small amounts of the substance, may cause further inflammation and damage and so on.
Allergic contact dermatitis
This occurs when your immune system reacts against a specific substance. The substance is then called an allergen. You only need a small amount of allergen in contact with your skin to cause the rash.
You are not born with this type of allergy - you must have previously come into contact with the allergen which has sensitised your immune system. Once sensitised, your skin reacts and becomes inflamed when it comes into further contact with the allergen. This is why you can suddenly develop a skin allergy to something you have come into contact with many times before. It is not clear why some people become allergic to some substances and most people do not.
Many substances can cause an allergic contact dermatitis. Common ones include:
- Nickel - this is the most common cause. Nickel occurs in many types of metal. For example: jewellery, studs in jeans and other clothes, bra straps, etc. So it is common to develop itchy red patches on the skin next to such things.
- Cobalt - traces of this metal may be found in some jewellery.
- Cosmetics - particularly perfumes, hair dyes, preservatives and nail varnish resins.
- Additives to leather and rubber (in shoes, clothes, etc).
- Preservatives in creams and ointments.
- Plants - the most common culprits being chrysanthemums, sunflowers, daffodils, tulips and primula.
Sometimes the cause is not clear and you may need tests to find the cause (see below).
What are the symptoms of contact dermatitis?
Irritant contact dermatitis
The main symptoms are redness, burning, stinging and soreness of affected areas of skin. The onset of the skin reaction is usually within 48 hours of coming into contact with the irritant. Strong irritants can produce immediate reactions, whereas mild irritants require longer or repeated exposure to cause a reaction. The symptoms only occur on areas of skin exposed to the irritant.
Allergic contact dermatitis
The main symptoms are redness, itch and scaling of affected areas of skin. There is often a delay of many hours to several days before symptoms develop following contact with the allergen (the sensitising object or chemical). The site of the rash and skin symptoms is mainly where the contact had been. For example, eyelids and cheeks if the allergy is to a cosmetic. However, as it is a true allergy, other areas of skin that were not in direct contact with the allergen may develop a rash.
Can you have different types of dermatitis at the same time?
Yes. For example, you may be born with atopic eczema. Your job may involve frequent use of a solvent which may cause an irritant contact dermatitis. In addition, you may also develop an allergy to nickel and so find that you get patches of inflammation over jean studs, or if you wear cheap jewellery, etc.
Do I need any tests?
The cure for most cases of contact dermatitis is to avoid the offending substance. In many cases no tests are needed, as it is often clear which substance has caused the rash. However, sometimes it is not clear what is causing the rash. Or, it may be a substance which is an additive to various things and you cannot pinpoint what it is. This is where patch testing may be advised.
Patch testing helps to find the cause of allergic contact dermatitis. You need to be referred to a dermatologist (skin specialist) for patch testing. They will place a small amount of various substances that may be causing the rash on to your skin. This is usually done on the skin of your back, in sets of 10. The skin is then covered with an adhesive dressing.
After two days the dressing is removed and the skin is examined to see if there is a reaction to any of the tested substances. The skin is also usually examined again after a further two days in case you have a delayed reaction to any substance. Sometimes the skin may be examined again a week after the initial substances were put on your skin.
If no skin reaction occurs on patch testing then this can also be helpful to rule out allergic contact dermatitis as a cause of your skin problem.
What is the initial treatment for contact dermatitis?
As mentioned, the main treatment is to avoid the offending substance. However, your skin may also be sore, itchy and scaly so various initial treatments may be suggested to help clear your symptoms.
If the inflamed skin is not too bad then just using an emollient (moisturiser) frequently may be all that you need until the inflammation settles and the rash clears. Soap substitutes may also be suggested.
Topical steroids are creams, ointments and lotions which contain steroid medicines. They work by reducing inflammation in the skin. They come in different brands and strengths. As a rule, you should use the mildest one that works. You can buy a mild steroid cream (hydrocortisone) without a prescription from pharmacies. If a mild one does not work, a stronger one can be prescribed by your doctor.
Topical steroids are usually applied once or twice twice daily in a thin layer on the affected area until the inflammation has gone. This may take up to a couple of weeks or more. Once the inflammation has gone, stop the topical steroid. You should wait for several minutes after you have used an emollient (moisturiser) before you apply a steroid cream.
Short courses of topical steroids (less than four weeks) are usually safe and usually cause no problems. Side-effects may develop if topical steroids are used for long periods, or if short courses are repeated often. The main concern is if strong steroids are used on a long-term basis. Most people with contact dermatitis only need a short course. See separate leaflet called 'Topical Steroids for Eczema' for more details.
An antibiotic may be prescribed if the inflammation becomes infected. This is uncommon in most bouts of contact dermatitis. Rarely, a course of steroid tablets is needed if you have a large and severe area of skin inflammation.
Rarely, steroid treatment does not clear contact dermatitis and other treatments may be suggested. These may include tacrolimus cream and treatment with medicines such as azathioprine, ciclosporin or oral retinoids. Ultraviolet (UV) light exposure, sometimes helped by taking a medicine called psoralen, is also sometimes recommended. This is known as psoralen combined with ultraviolet A (UVA) treatment (PUVA). Grenz rays (low-energy electromagnetic rays) are sometimes used when other treatments fail.
What is the long-term treatment for contact dermatitis?
Once the inflammation has settled, the main aim is to prevent it from happening again.
Avoid the cause
If the offending substance can be identified, then if you can avoid it, the dermatitis will usually clear and not return. (There are some exceptions. For example: irritant contact dermatitis caused by chromium in cement can sometimes lead on to a long-term skin rash - even if the contact with chromium stops.)
Avoiding an irritant or allergen may be easier said than done. For example:
- Some substances which cause allergic contact dermatitis are additives to everyday things such as leather shoes and clothes, rubber, metals, cosmetics, etc. They may be difficult to avoid fully. However, your doctor or skin specialist can give you advice on where the substance is likely to occur and how to avoid it.
- For some people, their job involves using substances that can cause irritant contact dermatitis. Unless you change your job, you may not be able to avoid the substance completely. Good hand care (described below) may help.
About 3 in 4 cases of contact dermatitis involve the hands. Many cases are due to irritants (rather than allergies) from chemicals or other substances used at work. To help prevent irritant contact dermatitis of the hands, get into a routine of good hand care:
- Don't keep your hands in water for very long.
- Use protective gloves wherever possible when working with chemicals, detergents, etc.
- Consider using a barrier cream to help protect the skin on your hands when working.
- Use a mild skin cleanser rather than soap to clean your hands.
- Dry your hands thoroughly after washing.
- Use lots of moisturising cream and apply it frequently. This helps to keep the skin on your hands supple and to prevent chapping.
Intermittent use of topical steroid
Topical steroids will ease a flare-up of symptoms but are not a long-term cure for contact dermatitis. The only long-term cure is to identify the cause and to avoid it.
However, it may be useful to have a topical steroid in your home medicine box. You may develop a flare-up of symptoms if you accidentally come into contact with a substance you are allergic to. For example, if you use a new cosmetic or some jewellery which you did not realise contained your allergen. A short course of topical steroid will then be welcome to ease the rash and inflammation.
Further help and information
National Eczema Society
Hill House, Highgate Hill, London, N19 5NA
Tel (Helpline): 0800 089 1122 Web: www.eczema.org
Further reading & references
- Diagnosis, management and prevention of occupational contact dermatitis: concise guidelines; Royal College of Physicians and British Association of Dermatologists (2011)
- Dermatitis - contact, Prodigy (September 2008)
- Dermatitis and other skin disorders: statistics; Health and Safety Executive
- Bourke J, Coulson I, English J; Guidelines for the management of contact dermatitis: an update. Br J Dermatol. 2009 May;160(5):946-54. Epub 2009 Mar 19.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Tim Kenny
Dr Laurence Knott
Dr Tim Kenny