Kidstuff Kidstuff By Paul L. Marz, M.D.
Hey mom! I've got a rash!
So you wander over and take a look. Hmm, it's on the arm. Let's look under your shirt. And it's on your chest! The worry grows, as this must be something SERIOUS!
Well, just slow down and look at this rationally. How is the child doing over all? No fever? Feeling fine? A bit itchy maybe, but just fine.
Now, what does the rash look like? Is it all over the child, or is it just under and around the edges of that shirt? Off comes the shirt and it sort of looks like the rash is everywhere the shirt was; but everything else is fine.
Welcome to the world of contact dermatitis. The patterns can be anything, but there is a pattern.
Dermatitis is Latin for skin (derm) that is red, hot, and itchy (itis). The contact part of the word means that whatever is doing this has made contact with the skin somehow from somewhere.
You can narrow down the possible causes by looking for the pattern of the rash. Possible contacts could be fabric softeners, (so under the diaper is fine), shampoos, (streaking down back and chest), makeup, metal fasteners, and the list goes on. All of these things are not corrosive or damaging in themselves.
How does this happen? First, let's look at what skin is. Skin is the biggest organ of the body and is just about everywhere. Its job is to keep the inside in and the outside out. It is the body's first layer of defense.
The top, dead layer of the skin is the epidermis. This is the layer that makes up calluses. Remember getting a skin scrape and peeling off the top layer without bleeding? The epidermis is not alive so it can take a fair amount of abuse before you even know about it. Your body is making more of this stuff all the time.
With contact dermatitis, the contact must happen for the rash to start. Let's use a nickel allergy. For those with this allergy, any skin contact will result in an itchy red raised area. The exposure is slow, and you need a little moisture to move the material through the "dead" epidermis. The epidermis is replaced from below by the "live" dermis layer and this part of the skin is what provides the reaction.
Once the nickel makes it to the dermis, it triggers an allergic release of histamine. This chemical signal causes the nearest blood vessels to leak a little fluid; not blood, just a bit of the clear fluids in the blood. This fluid causes the skin to expand, and you see a little swelling. Since the nickel trigger keeps things going off, the bump on the surface gets bigger, itchier and angrier The skin feels it is under attack and must work fast to protect and defend. With contact dermatitis, the body itself is fine; it is just reacting to outside forces.
So, when the fashionable young patient we've quoted above complains of a tummy rash, it turns out to be right around the spot where the button of her jeans would sit. Aha! As we said, always look for the pattern. Wise mom just paints the back of the metal snap with nail polish. Metal contact eliminated, the rash goes away.
For more involved areas or rashes that itch, use diphenhydramine or benadyrl as directed by the package.
However, if you have done your best and the rash is still there (along with the child's complaints) it's time for a visit to your doctor
(Dr. Marz, a board certified pediatrician, is supervising physician for the Town of Barnstable school system. He practices with Bass River Pediatrics in South Yarmouth.)