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Contact Dermatitis: More Than You Ever Wanted to Know

Contact dermatitis is simply inflammation that results from the interaction of skin and an external substance (even water) that comes in contact with it. It is an altered state of skin reactivity induced by exposure to an external agent. For the vast majority of people, these substances are harmless. “Eczema” and “dermatitis” are often used synonymously to denote a polymorphic pattern of inflammation of the skin. In all cases the lesions of contact dermatitis are primarily confined to the site of contact. Contact dermatitis can look – and itch – very much like eczema. It usually presents as a rash of tiny blisters, inflamed reddened skin, sometimes dry, or sometimes moist and oozing.

Contact dermatitis is produced through one of two major pathways: irritant or allergic.
Irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD) are two of the most common dermatologic conditions in industrialized societies, with a prevalence of up to 10%. The two conditions are clinically indistinguishable and often both conditions co-exist. Many of the allergens causing ACD are also irritants.
Irritant contact dermatitis predominates, accounting for 80% of all cases of contact dermatitis. ICD is a non-immunologic skin reaction that does not involve immune system sensitization (previous exposure to the allergen). It can occur in all members of the population depending on the “irritancy” of the chemical, the duration of contact and individual susceptibility. Atopics (who invariably have dry skin) are more prone to irritant dermatitis. Water is one of the most common irritants; therefore atopics who do a lot of wet work will often get irritant hand dermatitis. Another reason atopics get irritant dermatitis is that the skin gets injured from chronic scratching, allowing the otherwise harmless chemicals in cosmetics to enter the skin. The most common skin irritants include acids, alkalis, detergents, and solvents that disrupt the barrier function of the skin. Common cosmetics / skin care products causing skin irritation include:

• Bath soaps & shampoos
• Eye shadow & mascara
• Make-up removers,
• Antiperspirants,
• Permanent hair-waving solutions.
• Water present in cosmetics and skin care products is the most common irritant to very dry skin.
Irritant contact dermatitis is a risk factor for allergic contact dermatitis, as the penetration of contact allergens is enhanced when the skin barrier function is disturbed.

Allergic contact dermatitis (ACD), on the other hand, is an immunologic skin reaction that occurs in a genetically predisposed individual. The allergic response occurs only when a person’s immune system is sensitized to the allergen. The more contact the individual has with the allergen the greater the risk of sensitization. In sensitized individuals, allergic contact dermatitis appears or is exacerbated 24 to 96 hours after contact with the causative allergen. ACD is usually accompanied by intense itching. The edges of the lesions are usually well demarcated, but unlike irritant dermatitis it may propagate beyond the site of contact. This reaction is also known as delayed hypersensitivity reaction, since the rash usually develops more than 12 hours after contact with the allergen. The reaction usually peaks about 48 hours after exposure. The number of chemicals known to be capable of causing ACD is said to be near 3000 and constantly increasing.

Site of the skin reaction is usually the face especially around the eyes. In one study allergic contact dermatitis was found to be the cause in 74% of patients with eyelid dermatitis. In Saudi Arabia it is well known that men with dermatitis in the beard have an allergy to permanent hair dyes.
Common allergens in cosmetics and skin care products that cause contact dermatitis
Current reviews demonstrate that the most frequent allergenic groups causing cosmetic allergy are fragrances, preservatives, and paraphenylenediamine (PPD) found in permanent hair dyes.

The commonest allergen causing ACD is fragrance. More than 5000 different fragrances are used in cosmetics and skin care products. Seventy to eighty percent of fragrance allergy can be picked up by patch testing with Balsam of Peru and Fragrance Mix (which contains 8 common fragrances). Fragrance can also cause increased pigmentation of the affected skin, photodermatitis, or contact urticaria.
It is important to know that “unscented” does not mean “fragrance-free”. Some unscented products might contain a fragrance to mask other chemical odours. To indicate that no fragrance is added to a product it must be marked “fragrance-free” or “without perfume”.
In 1989, less than 10% of the patients patch tested in a multicentre project in Germany reacted to the fragrance mix (a mixture of 8 important fragrances). Between 1990 and 1994, a steady increase in the percentage of sensitizations diagnosed to more than 13% was noted (4).

Screening for Fragrance Allergy:
These are the fragrances tested in a standard patch test battery:
• Balsam of Peru
• Fragrance Mix:
1. Oak Moss
2. Cinnamic aldehyde
3. Cinnamic alcohol
4. Alpha amyl cinnamic alcohol
5. Geraniol
6. Hydroxycitronellal
7. Isoeugenol &
8. Eugenol

• Musk Ambrette and Moskene
In a worldwide multicenter investigation on fragrance contact dermatitis, reaction to fragrance mix occurred in 78% of patients patch tested
Balsam of Peru
Balsam of Peru (BP) is usually included in the standard screening patch-test series as an indicator of fragrance sensitivity. It is positive in 50% of cases of fragrance allergy. BP is a naturally occurring substance, obtained from fir trees. It is composed of many allergens including benzyl acetate, benzoyl alcohol, cinnamic acid, cinnamic alcohol, cinnamic aldehyde, eugenol, and isoeugenol.

Paraphenylenediamine (PPD) Hair dye Allergy
This is the most important dye used for permanent (oxidation) hair colouring and is the third most common ingredient after fragrances & preservatives that cause contact dermatitis from cosmetics. Permanent hair dyes are more sensitizing compared to other types of hair dye.
In most cases the reaction to the dye is itching of the scalp and some redness, but nothing more. These individuals might just think they have a bit of dandruff. In more severe cases the hair dye may trigger scaly skin & pain. The distribution of the affected skin can vary and may not match the exact area to which the dye was applied. In more severe cases there can be swelling around the eyes and scaly skin on the ears, face & neck. Sensitization to hair dye may gradually develop with repeated exposure.
In some European countries, PPD was banned because it was thought to be too hazardous. The regulations of the EEC, however, have allowed up to 6% PPD in hair dyes.
In the consumer, PPD produces acute dermatitis that involves the scalp, eyelids, face, and hairline and may extend to include the neck & upper portion of the trunk, but may spread to involve the whole body. In the hairdresser the most common region affected is the hand, but other exposed areas like the arms & face may be affected. Once the dye becomes fully oxidized it is no longer allergenic; thus dyed hair does not cause dermatitis.
Other damage to the scalp skin can make one more sensitive than normal to hair dye and other chemicals.

Substances related to PPD which should be avoided in PPD-sensitized people
• Benzocaine (found in some haemorrhoid preparations) & procaine – local anaesthetics.
• Azo dyes: used in temporary & semi-permanent hair dyes, pen inks,
• Textiles dyes – especially dark clothing & clothing made of synthetic fiber like polyester or nylon
• Some foods & pharmaceuticals coloured with azo dyes
• Sulfa drugs
• Para-aminobenzoic acid (PABA) – found in sunscreens

Hair dye open skin sensitivity Test (“Dab test”) or Open Patch Test
In many countries there is legislation that requires hair dye products to carry a warning about conducting patch test prior to using the dye. This is a precaution to make sure the individual is not sensitized to the dye.
Allergies to PPD can develop, even though there was no reaction during previous use. For this reason, it is important to take the allergy test 48 hours ahead of every use.
The test area used is either behind the ear or inside the arm at the elbow. A small amount of the “colour base” (or some companies recommend mixing the base with the developer first) is applied to the test area. Do not wash the test area. Wait 48 hours unless there is reddening, burning or other irritation. If there is no reaction on the unwashed patch test site after 48 hours, then one can proceed to the full application.
Three dermatological departments in Italy, Great Britain & Poland, have validated this test. They considered it an effective method to detect delayed hypersensitivity (contact allergy) to hair dyes, and as such are useful in the secondary prevention of hair dye allergy. (5)

Preservatives in cosmetics and skin care products are the second most common cause of skin reactions. Cosmetics that contain water must contain some preservative to prevent bacterial or fungal growth. Examples of cosmetics preservatives that cause allergy include:
• Parabens are the most commonly used preservatives in cosmetics
• Formaldehyde is an important sensitiser & is released by a number of biocides, it is mainly found in shampoos
• Imidazolidinyl urea (Germall 115)
• Quaternium-15 (Dowcill 200) is a formaldehyde releasing preservative found in many cosmetics including, eye makeup, foundations, shampoos, moisturizing lotions, sunscreens, body powders, and skin cleansers.
• Phenoxyethanol
• DMDM hydantoin (Glydant)

Cocamidopropyl Betaine (CAPB) was voted Contact Allergen of the year for 2004 by a committee of international experts. It is a non-ionic surfactant found primarily in rinse off cosmetics (shampoos, soaps, and bath gels). It is less irritating to the skin than older surfactants. For this reason patients may think that a less irritating product such as a baby shampoo is safer for the skin when it is more likely to cause allergic contact dermatitis.
A case was presented in the American Journal of Dermatology (Vol 15, No 1 (March), 2004: pp3-4) of a 37-year-old woman who presented with eyelid dermatitis that had been present for 5 months. She was instructed by her family doctor to apply baby shampoo to the eyelids daily (similar advice given in NZ as well). Patch testing revealed a + reaction to CAPB. CAPB was present in the baby shampoo she applied. Discontinuation of this product resulted in clearing of her allergic contact dermatitis.
CAPB is found in over 600 personal care products (according to FDA). The case of CAPB illustrates an important point regarding allergy to cosmetics. Because CAPB is “less irritating” than other surfactants, it may be preferred by consumers, manufacturers, and doctors. The fact that it is more allergenic came to light only after its widespread use.
The reported prevalence of allergic contact dermatitis (ACD) secondary to CAPB exposure ranges from 3.0 to 7.2% (6).

Lanoline or Wools alcohol
In North America lanoline was the fourth commonest cosmetic allergen (after fragrance, preservatives and PPD) causing contact dermatitis (7). It is felt that the prevalence of ACD to lanoline is decreasing because knowledge of its allergenicity has been known for a very long time.
It is a natural material obtained from the sebum of sheep. It is recovered from raw wool by solvent extraction. It is used in cosmetics because of its emollient, moisturizing, and emulsifying properties.
There are several allergens present in lanoline, and lanoline-sensitive patients can sometimes tolerate one lanoline preparation but not another.

Cosmetics containing lanoline include:

• Moisturizers, Hand creams, Protective creams
• Sunscreens
• Glossy lipsticks
• Makeup remover, Eye makeup
• Foundations, eye makeup
• Baby oils & diaper lotions
• Hair spray

Cosmetics with herbal ingredients
Virtually all-herbal remedies have been reported to cause either allergic sensitization or photosensitization.
In a recent study in Portland, Oregan, USA, 63% of patients with suspected cosmetics dermatitis that had used a skin product containing botanical extracts were patch test positive to a botanical extract. In New Zealand the true prevalence of contact allergy to botanical extracts in patients with cosmetics dermatitis is unknown, as most people who suffer from skin rashes do not seek medical help unless the rash is persistent.
Common herbal products causing contact dermatitis include plants from the Compositae family:
• Artichoke
• Chamomile (found in numerous shampoos & other hair treatment products)
• Daisy (Chrysanthemum)
• Dandelion (Taraxacum)
• Feverfew
• Marigold
• Pyrethrum
• Ragweed (Ambrosia)
• Thistle
Several plants in the Compositae plant family are regularly included in “natural skin care products” in New Zealand, especially shampoos and aromatherapy solutions. In some cases the reactions to Compositae is worsened by sunlight, often giving the appearance of a light-sensitive rash.

Tea Tree (Melaleuca alternifolia) Oil is increasingly being used in NZ in various cosmetics (soaps, deodorants, toothpaste, gargles & aftershave) and allergic contact dermatitis is being found related to this product throughout the world.
The leaves of the tea tree contain an essential oil, which contains turpentines (limonene, alpha-pinene, phellandrene). In one study in Honolulu limonene was the most common allergen causing allergic contact dermatitis from tea tree oil.
The ‘tea tree’ oil available in the Netherlands is distilled from the Melaleuca alternifolia and mainly contains eucalyptol. Eucalyptol is probably the most important allergen. The Photoaged Melaleuca is a stronger sensitiser than regular tea tree.
There have been recent reports of topical tea tree oil causing anaphylaxis (Allergy Asthma Proc. 2003 Jan-Feb; 24(1): 73-5)
There are reports in the literature describing several individual cases of contact dermatitis in patients using propolis as a component of various cosmetic products, listing the most frequently sensitizing constituents of propolis. There are also reports of the existence of a cross-reaction between the components of Peruvian balsam and propolis constituents.

Henna Allergy
With the vigorous back-to-nature trend in Western countries, henna as a natural hair dye has become increasingly popular. This shift away from chemical dyes is enforced by the relatively high risk of sensitization to chemical dyes, in both hairdresser and their clients.
Henna is derived from a shrub Lawsonia inermis, which is native to the Middle East & North Africa.
There have been several reports in the literature of Immediate Allergic (& Anaphylactic) reaction to using Henna hair dyes. Most cases had sneezing, runny nose, cough, & shortness of breath instead of skin reactions. They were all diagnosed with the help of a positive skin prick test to henna extract. Most of these individuals were hairdressers who became sensitized from their work. It is felt that they became sensitized by inhalation of henna powder dispersed in the air.
Henna also causes allergic contact dermatitis.

Photosensitivity is the term used to describe skin disease caused by the interaction of UV radiation and an exogenously (externally) acquired chemical agent, which may be either a drug or food taken orally, or a substance applied to the skin. It can be divided into photodermatitis, also referred to as photoallergic dermatitis, and photoirritant contact dermatitis.

Plants that cause photodermatitis (Phytophotodermatitis)
Phytophotodermatitis produces reddening and blisters on first exposure followed by persistent hyperpigmentation (darkening of the skin). This darkening of the skin can last for months. The rash is produced via a phototoxic reaction, which simply means that the reaction renders the skin susceptible to damage by UV light, and symptoms include burning pain at the affected site. This is in contrast to the reaction produced by plants such as poison ivy, which is classified as allergic contact dermatitis, and involves symptoms such as intense itching.
Compounds related to furocouramins (psoralens) usually cause plant-related photosensitivity. Two requisites for initiation of phytophotodermatitis are contact with a sensitizing plant (e.g. furocouramin) and exposure to ultraviolet light (wavelength greater than 320 nm), usually sunlight. Therefore, this dermatitis is usually seasonal.

Common plants causing photodermatitis:

Common Name
Botanical Name
Angelica archangelica
Citrus bergamia
Apium aurantium
Citrus medica
Anethum graveolens
Foeniculum vulgare
Ficus carica
Citrus lemon
Citrus aurantifolia
Pastinaca sativa
Wild Carrot
Dacus carota

In New Zealand many of these plants are also being added to “natural skin care products”.
Contact urticaria is a hives-like reaction occurring at the site of contact of the skin product and usually occurring within 15 minutes of the product touching the skin.

Diagnosis of skin rashes caused by cosmetics
Contact Urticaria is diagnosed by applying the product to the skin for 15 – 20 minutes and observing the skin for redness, swelling and itching or doing a skin prick test (applying the suspected allergen/s to the forearm and pricking the skin with a lancet & waiting 15 minutes for a bump like a mosquito bite at the site of the prick)

Contact Dermatitis is diagnosed by doing a patch test. The only way to obtain proof of allergic contact dermatitis is by patch testing. Patch testing is the universally accepted method for the detection of the causative contact allergens. The positive patch test reproduces an experimental contact dermatitis on a limited area of the skin. This is different from skin prick testing (which gives a positive response in 15 minutes) in that it is a delayed hypersensitivity response (it gives a positive response in about 48 hours).
The most frequently encountered contact allergens have been selected by various international contact dermatitis groups and included in standard patch test series. The chemicals are taped to the back in small chambers. The skin is not broken. The patches stay in place for 48 hours. You cannot shower or do any work or exercise that will wet or loosen the patches.
After 2 days, the patches are removed, and a reading is done. The patch sites are marked, and you may be asked to return for a final reading on another day. An experienced doctor can differentiate between allergic contact dermatitis and an irritant reaction on patch testing.

Repeated Open Application Test (ROAT) or Use Test
This is a simple test for new skin care products or products suspected of causing skin reactions. A small amount of the product is applied twice daily to a small area of normal skin, usually on the front of the elbow for 1 week. If no rash appears after 1 week the product is considered safe for that individual. This test simulates the everyday use of cosmetic products and can be used to define the clinical relevance of doubtful or positive diagnostic patch tests.
Photo-patch testing is patch testing with the addition of radiation to induce the formation of photoantigens. All photosensitive patients should be photo-patch tested.

Cosmetic Allergy & The Future
A recent Patch test study done in Austria (published in Paediatrics Dermatology 2003 Mar-Apr; 20(2): 119-23) showed that the overall sensitization rate was highest in children less than 10 years old (62%) and decreased steadily to be lowest among patients more than 70 years old. This coupled with the fact that appearance is so important to adolescents as they are bombarded with numerous cosmetic advertisements; they are significant consumers of toiletry & skin care products. Therefore we would expect the prevalence of cosmetic allergy to continue to increase.

(1) Allergic contact dermatitis to topical minoxidil solution: Etiology and treatment. J Am Acad Dermatol 2002; 46:309-12
(2) Dooms-Goossens A et al., Cosmetic products and their allergens. Eur J Dermatol 1992; 2: 465-8
(3) Kohl, et al, Allergic contact dermatitis from cosmetics. Retrospective analysis of 819 patch-tested patients. Dermatology. 2002; 204(4): 334-7
(4) Wolfgang Uter et al. Epidemiology of contact dermatitis. The information network of Departments of Dermatology. European Journal of Dermatology. Vol 8. Number 1. 36-40 Jan – Feb 1998
(5) Maya Krasteva et al. Contact Sensitivity to hair dyes can be detected by consumer open test. European Journal of derm. Vol. 12. Number 4, 322-6
(6) Joseph F. Fowler Jr et al. Allergy to Cocamidopropyl Betaine and Amidoamine in North America. Dermatitis, Vil 15, No 1 March, 2004: pp5-6
(7) Adams et al. A five year study of cosmetic reactions, J Am Acad Dermatol 13: 1062-1069, 1985
Contact & Occupational Dermatology by James G. Marks & Vincent A. DeLeo