There are two main types of allergies-those that you see and feel on your skin and internal allergies caused by the ingestion of an allergen specific to your makeup. Sometimes an internal allergen can present itself on your skin, while an external allergen can cause internal symptoms. An allergy physician, or an allergist, can determine where and how the allergen made contact with you and how best to treat your reactions.
Contact Dermatitis vs. Allergic Reaction from Within
Contact dermatitis is a strictly, skin-only allergic reaction to something on your skin. It has quite a different look and texture to it than an allergic reaction that starts from within your body and surfaces on your skin. When you are referred to an allergist, the allergist can take one look at the rash on your skin and know right away whether it is a contact dermatitis situation (like poison ivy) or an internal allergic reaction. If he diagnoses you with a contact dermatitis rash, then you need to avoid a number of things that your skin touched in the last twenty-four hours and he or she will prescribe a topical medication. If it is an internal allergen causing your skin to flare up, then the next steps are a little more complicated.
Internal Allergic Reactions Presenting Themselves on Your Skin
When the allergist knows or suspects that the reaction on your skin is the surfacing of a deeper allergic reaction to something internally, he or she will perform some tests. Sometimes a "scratch" test will look for common allergens, testing you for any number of allergens that could cause a rash to surface on your skin after ingesting something. At other times, the allergist may just prescribe a round of antihistamines or a short-term round of corticosteroids to eliminate the effects of the allergen quickly. If your body responds to the medications, then the doctor knows with absolute certainty that you ingested something you should not have, and these medications work well enough for you that you can keep some on hand to treat another flare-up in the future.
Taking an Ingestion History
The allergist (for future reference) may take an ingestion history as well. Anything that you have consumed in the last twenty-four to forty-eight hours that was out of the ordinary for you should be included, since many people discover that they have a food or drink allergen only after they have consumed it for the first time. From this history, the doctor can choose to perform additional tests that could benefit you in the future by alerting you to your unknown allergens and preventing you from taking them internally. In doing so, you will also avoid any further dermatological abnormalities that accompany your internal allergies.