The Skinny on Common Skin Allergies

Health Professional, Medical Reviewer

Did you know the largest internal organ of the body is the liver? But the overall largest organ of the body is the skin. It's no wonder the skin is involved with so many aspects of diseases: rash, itching, fever, external bleeding, swelling, pallor (turning pale), and cyanosis (turning blue). Doctors look for signs of hundreds of diseases by examining the organ that is most accessible, the skin.

Often the skin is our first line of defense against adverse conditions such as hot and cold temperatures, external trauma (for example falling on hard ground) and harmful rays of the sun. We are protected from a myriad of germs (bacteria, viruses, fungi and parasites) by having a finely woven coat of armor, our skin.

Unfortunately certain substances, after contacting the skin, may cause a break down in protective barrier forces. This may be followed by inflammation and a skin eruption (rash) that signals the development of contact dermatitis (CD).

Contact dermatitis may occur at any age but is more common in adults. It is just as common in non-allergic people as in those who suffer from allergic rhinitis or allergic asthma, so a family history of allergy doesn't place you at higher risk for this ailment. CD can be grouped into two categories, allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD). ACD occurs when contact with a substance causes a sequence of cellular events that involve the immune system resulting in a skin rash.

ICD does not involve immune cellular events and generally occurs within seconds to minutes after the skin is exposed to the irritating chemical or compound. Reddening of the skin, mild burning, scaling and possible further discoloration may occur. Soaps and detergents most commonly cause ICD. The classic is "dishpan hands" which can result from prolonged or frequent exposure to household cleaning products.

What is the difference between Allergic and Irritant Contact Dermatitis? In ACD there is a sensitizing period (the time between initial exposure and becoming hyper-sensitive) that may range from days to several months. Exposure to the same substance after the sensitizing period results in a skin reaction that may occur 12 to 48 hours later (** often called delayed allergic reaction**). The sensitivity usually lasts for several years.

What are some causes of Contact Dermatitis (ACD)?

Some common causes of ACD include nickel, other metals, poison ivy, hair dye, rubber (from latex protein), citrus fruits (especially in the peel), chemicals in leather, medicated creams, other pharmaceuticals, cosmetics, perfumes, skin cleansers and jewelry.

Nickel is the most common metal associated with ACD. Nickel is widely use used in the clothing, jewelry and apparel and is difficult to avoid. The metal snaps and zippers on pants, coats, jackets and some shirts often contain nickel. Other items that may contain nickel include: belt buckles, hair pins, kitchen utensils, tattoo ink, dental fillings, artificial body implants (for knee, hip, shoulder replacement), household tools, eyeglass frames and audio ear pieces and even cellphone encasements. I wish I could say the above list is complete but it's not.

Hair dye is another common cause of ACD. The most common culprit in these products is paraphenylenediamine (ppd). This chemical is widely used in permanent hair dye, textile and fur coloring, in some ink, temporary tattoos, and gasoline (an incomplete list).

The rash associated with hair dye often develops at the base of the neck, forehead, upper eye lids, and rim of the ears. It appears as a reddening and swelling that may be accompanied by fine bumps. Involvement of the scalp and face may follow the initial appearance of the rash. Severe reactions to ppd may result in the development of hives and rarely, anaphylaxis (possible throat swelling, difficulty breathing and/or passing out).

How is ACD Treated? First, the cause of ACD should be identified by seeing your doctor. Patients are often referred to allergists or dermatologists for more difficult cases. Dermatologists and some allergists may do** patch testing** in order to determine what the sensitizing agent is. Once the culprit is exposed (if the patch test is positive) the patient must avoid further contact with the substance by learning about where it is usually found.

Topical steroids and occasionally oral steroids are prescribed for treatment of the skin rash associated with ACD. Sometimes antihistamines are also given in order to reduce itching.

The key to managing ACD is identifying the cause. This is often the greatest challenge for your doctor. You can assist your physician by carefully retracing your steps if you develop a bothersome skin rash. While fresh on your mind, you should detail (in writing) everything that you have contacted (in the area of the skin eruption) starting 48 hours before the onset of symptoms. Bring the list, and any cosmetics or medications with you to the doctor's office.

Have you ever had contact dermatitis?** What was the cause?**