Archive for Skin Allergies and Patch Testing

Allergic Contact Dermatitis

Are you itching to know what might be causing your skin rash?  If you have eczema or dermatitis, you might be allergic to something your skin has come in contact with.  Sometimes the allergen is fairly obvious, such as if you got exposed to poison ivy.  Many times however which chemical allergens are involved is not obvious.  Since avoidance of the allergens can often result in significant improvement or clearing of the rash, finding out what you might be allergic to is important.  The allergen testing process is called patch testing.  It is different from the scratch and prick testing that allergists do.

Patch testing involves having panels of allergens applied to the skin of your back and taped in place.  They are left in place for two days.  The tapes are then removed and a first reading is done.  A second reading is done a day or two later because the reaction is often delayed. During the patch testing process you cannot get your back wet.  After the second reading, you will receive a printout listing any allergens and what products would be safe to use. 

After you begin avoiding your allergens, the allergen you already have bound to your skin will slowly be shed, usually over 6 to 8 weeks, and you may begin to notice improvement or clearing of your dermatitis type rash. You will remain allergic to those allergens and will have to continue to avoid them.  For many people the relief obtained is significant and lasting.

by:Philip Shenefelt, MD

Dr. Shenefelt is Professor and Dermatologist at USF Health and actively see patients at the Morsani Center for Advanced Health Care on the USF campus and also at the USF Health Davis Island location. For appointments call 813-974-4744

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Skin Health Hazards from Crude Oil Spill

While our skin is a marvelous barrier that keeps us protected and minimizes absorption of most toxic chemicals, it was not designed to deal with crude oil or tar balls.  The volatile components of crude oil can irritate the skin producing redness and dryness and can also be absorbed to a limited degree.  They can also produce eye irritation. The heavier tarry components of crude oil can stick to the skin and produce mild irritation. They can also coat hair. When the crude oil has been exposed to the air for a while, most of the volatile components evaporate, leaving tar balls.  The tar balls can stick to our skin and hair. The detergent-like dispersants used to treat oil escaping from a ruptured oil well can also irritate the skin if they are in high enough concentration in the water.


The best approach is for you, your children, and your pets to avoid contact with crude oil and tar balls.  Check the beach for any evidence of crude oil or tar balls and if present do not swim and avoid contact.  If you, your child, or your pet does get exposed, gently wipe off any crude oil or tar with paper towels and use soap or dishwashing detergent that cuts grease to cleanse the skin.  Shampoo or dishwashing detergent can be used on hair also, taking care not to let the soapy water run into the eyes.  Tar balls stuck to hair may require clipping the hair to remove the tar ball.  Once the skin is clean, use a good moisturizing lotion to treat dry skin and use over-the-counter hydrocortisone cream to treat redness.  If redness is severe or does not clear after a few days, see your dermatologist.


By: Philip D. Shenefelt, MD., Associate Professor of Dermatology and Cutaneous Surgery at the University of South Florida

Click link below for Dr. Shenefelt’s Bio

Click link below for Radio Clip

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Winter itch is the curse of the changing season Photo

I’m sure many of you have noticed that your skin has become itchy since the recent cold wave hit our area. Our “snowbird” friends from up North are quite familiar with this phenomenon they call “winter itch.”

Are they bringing with them some exotic disease, or is it related to the cold weather that drives (and often follows) them here?

“Winter itch” is a common skin problem that is triggered by cold weather. The problem is much greater in colder climates where they use more heat and the humidity is lower. Nonetheless, it also occurs in the South, especially when these more severe cold waves pass through.

Recently, I observed in many of my patients the telltale signs of winter itch characterized by dry skin, most notable on the lower legs and the arms, dry and cracked nail cuticles, chapped lips and many scratch marks. When queried, they all complained of itchy skin.

The cause of winter itch is well known. It is due to rapid and excessive dryness of the skin that occurs as winter descends upon us. During winter the humidity is lower; when the heat is on, the warm circulating air tends to dry the skin further. Simply remember how dry your skin got the last time you traveled North in the winter!

Moreover, when it’s cold outside many of you love to take a long, hot shower or bath — but this can actually aggravate your condition. What happens is that your waterlogged skin dries out due to the effects of evaporation, which is accelerated as the humidity decreases and the household heat increases. Since evaporation is a drying process, it is imperative to prevent it by applying a moisturizer within five minutes of towel drying. That will lock in the residual moisture.

Over time this will rehydrate your skin as well. If winter itch gets out of hand, your skin can become inflamed, resulting in “xerotic” eczema. The process is much worse if you have preexisting dry skin due to aging or atopic eczema (a common skin disorder characterized by sensitive skin associated with asthma and hay fever).

Here are some tips to prevent and/or treat “winter itch:”

• Turn down the thermostat.

• Avoid hot showers & baths (they degrease the skin).

• Limit bathing to five to10 minutes (less water, less evaporation).

• Use super-fatted soaps (fewer suds) or, better yet, soap-free cleansers.

• Pat dry and immediately apply a moisturizer while skin is still wet!

• Moisten and reapply moisturizer as necessary.

• Avoid irritating clothing (wool).

• If the skin is inflamed, apply 1 percent hydrocortisone cream, available over the counter.

• If the condition doesn’t resolve, see your dermatologist!

What do I look for in a moisturizer?

• It doesn’t have to be expensive to be good! (Same ingredients, different packaging.)

• Heavier is better (Less water-less drying via evaporation)

• Fragrance free better (Avoids allergens)

• Basic moisturizers are petrolatum based with emulsifiers. (They trap water in the skin by occlusion. Cost effective!)

• Enhanced moisturizers contain alpha hydroxyl acids, urea and hyaluronic acids. (They hold water in the skin and help normalize the damaged epidermis.)

• Pure petrolatum lip balms are best. (The more ingredients, the greater the risk for allergies.)

Dr. Fenske is professor and chair of the Department of Dermatology and Cutaneous Surgery at USF Health.

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