There are a range of causes and conditions which will result in an allergic reaction of the skin. Many of these require only limited contact with a particular substance to bring the person out in an itchy, often sore, bumpy red skin. This is allergic contact dermatitis and the severity of the condition varies widely; it can just affect the part of the body which has come into contact with the trigger or, in severe instances, most of the body.
Contact dermatitis is a very common condition but is not always due to an allergy as such. The most common form is actually irritant contact dermatitis (ICD) which is subtly different (though often linked to) an allergic reaction. ICD differs from allergic contact dermatitis (ACD) firstly in that it is often caused by the kind of substances you might imagine would damage the skin. ACD on the other hand is an immune response which can occur even after being exposed to tiny amounts of the allergenic substance.
What makes it difficult to identify the cause of these skin allergies is there can be a significant delay (up to 48 hours) between contact and the symptoms occurring. In this article we look at some of the most common triggers, or antigen sensitisers, in the hope that this might help with narrowing down the possible causes of a skin allergy.
Nickel & certain other metals
Nickel, cobalt and chromium are all common causes of allergic skin reactions. Gold and silver allergies are possible but rarer.
Nickel is often responsible for what is termed jewelry (jewellery) allergy and it is used in mixture with other metals to make a wide range of things such as jewelry, buttons, bra hooks and the likes. Jewelry made from relatively pure (more than carrat) gold and silver is usually not allergenic, however, gold may contain sodium thiosulfate which can act as an allergen.
Chromium allergy is often caused by working with cement or from leather work boots / gloves. Cobalt also occurs in cement but is found in many blue dyes and even vitamin B12 medicines.
Perfumes & toiletries
Of all the thousands of fragrances used in perfumes and other toiletries it is actually only a small number that have been implicated in allergies. However, the combinations of these fragrances in any one product can be complex.
To identify which particular fragrance may be causing a skin allergy a test involving a mixture of the 8 most common allergenic fragrances was devised – the “fragrance mix”. For the record and so you can check the ingredients these are; cinnamic alcohol, cinnamic aldehyde, eugenol, isoeugenol, geraniol, alpha amyl cinnamic alcohol, hydroxycitronellal, oak moss absolute.
Balsam of Peru is another ingredient often used in perfumes and toiletries which can cause an allergic reaction.
Poison Ivy & other plants
In North America the poison ivy plant is synonymous with the rash it causes. Whilst the allergen is strong it is also usually easily identified. Other common plants also cause allergies but are often overlooked.
The daisy family are one of the most frequent causes of rashes. This includes dandelions, marigolds and chrysanthemums. Primroses, hydrangeas and normal ivy are also common causes.
Which part of the plant is responsible for the allergy varies; it can be the sap, leaves or pollen, depending on the species. Certain plant extracts used in herbal medicines and natural cosmetics may also be allergy triggers. The most likely offenders are tea tree, peppermint and lavender oil along with henna which contains PPD (see hair dye below).
Latex is by far the largest source of natural rubber and is used in a wide range of products such as gloves, condoms, balloons, toys and medical equipment. There are actually two kinds of allergic reactions to latex one of which is caused by the latex itself, the other by chemical additives used in its processing. The former can cause what is known as contact urticaria – itching and swelling almost immediately after the contact. The rash caused by the other chemicals may take up to a few days to appear.
The chemicals used in making dyes for clothing, fur and leather products are often the cause of skin rashes. This occurs when certain chemicals leach out of the fabric and come into contact with the skin. As many of the dyes and treatments used in fabric processing are water soluble this means body sweat can also release the chemicals, causing skin contact and a possible allergic reaction.
Whilst there are a very large number of different textile dyes used some are particularly associated with skin allergy. Azo dyes, which contain diazoic and coupling components, are the worst offenders, although these are not used much anymore. The disperse dyes used on synthetic fibres are the next most commonly associated group, and for some reason certain blue colorings have proved most allergenic.
Adverse reactions to cosmetics ranging from nail care products through to make up and anti-ageing creams are well documented. Whilst these are more likely to be the result of irritation to the skin, rather than an allergic response, there are plenty of known potential allergens used by the cosmetics industry.
As well as the previously mentioned fragrances, some of the most common allergy triggers found in cosmetics include preservatives such as quaternium which is 15 used in everything from tanning lotion and shampoo through to industrial products like paint. Other preservatives with a reputation used in cosmetics are MI (Methylisothiazolinone) and formaldehyde.
Another common allergen is lanolin which is frequently found in creams and lotions where it is used as a moisturiser. Despite its natural origin from sheep’s wool, the alcohols in lanolin are often implicated in allergic rashes.
Yet again there are a number of chemicals in hair coloring products which can trigger an allergic reaction. Whilst this can be system-wide, localized skin reactions are more likely. Such allergies affect around just under 2% of the population, although is actually quite a significant number of people. A wide variety of chemicals are used in the production of hair dyes, however, it is a relatively small group of these that are implicated in allergies.
The ingredient in hair dye that is most often associated with allergic reaction is para-phenylenediamine (PPD) often used in darker colorings. This can on occasion cause a local skin reaction, but has also been known to result in a severe allergic reaction and even anaphylaxis.
Another use of PPD is in “black henna” temporary tattoos. Whether these are legal or not is one issue, but also they carry a risk of causing skin damage and increasing your chanse of becoming permanently allergic to hair dye.
Whilst there are other chemicals used in different dyes it is possible that once sensitised to PPD a person may also have a reaction to some of these. Therefore, it is advisable to be tested with other dyes before continuing. Providing your reaction was not severe previously you can do this yourself by dabbing a small amount of the dye on your inner elbow and leaving it for 48 hours.
Ironically the raised awareness of the dangers of too much exposure to the sun have meant there have been an increase in the number of people suffering allergic reactions to sunscreens. This is not completely surprising as sun blocks share many of the same additives as cosmetics and toiletries. However, it is also possible that the allergy to sunscreen is caused by the active, protective ingredients.
One particular aspect of this kind of allergy that is specific to sunscreens is the phenomena of photo-contact dermatitis; this is where the substance (in this case sunscreen) only becomes allergenic when the area of skin is also exposed to sunlight. This is to be expected with a form of sun protection and can usually be identified by the areas of the body affected. Also it is usually easy to tell apart from sunburn.
It is an unfortunate fact that one of the most common causes of skin allergies are medicines applied to the skin. Certain ingredients common to many medicinal creams, gels, lotions, balms, ointments and patches can actually cause more of a problem than they cure.
It is often the case that it is the base of the medicine and not the active ingredient that causes the allergic reaction. These are often the same culprits as seen in cosmetics such as the preservatives or even fragrances.
However, this is not always the case and the actual medical component can be the cause. The best known of these is the antibiotic neomycin which is commonly found in a range of ointments, ear and eye-drops.
The local anesthetic benzocaine is another common allergen and is even used in haemorrhoid preparations – ouch! Even the key ingredient of aspirin (salicylate) can cause skin reactions when applied in topical creams.
Household products: cleaning, solvents, adhesives etc.
As you might expect many products around the house used for cleaning and DIY are a veritable cocktail of chemicals, some more noxious than others. Amongst the worst are cleaners, detergents, polishes and disinfectants. Many of these are labelled as irritants but there is less information about the possible allergenic effects of many.
It is generally good practice to wear protective gloves whilst handling any of these you think you might be allergic to. In addition it might be worth trying natural cleaning products made from ingredients such as lemon juice and vinegar or certified hypoallergenic products.