Allergies (HB)
Patients can really be allergic to anything. The allergen is simply a substance that has entered the body via some route and to which the body overreacts, treating it like a foreign invader.
The body attempts to deal with the allergen by dumping histamines into the body. Two major effects of histamines are to constrict the lower airways (in an attempt to limit the exchange of inhaled toxins) and to dilate the blood vessels (presumably to dilute the toxins in the vascular system). The local swelling, redness, and itching comes from dilated capillaries near the surface of the skin.
This allergen can be ingested in the form of food or drink, injected like a bee sting, or inhaled like pollen. It can also be from contact with a toxin like poison ivy.
Common allergens include bee stings, tree nuts, shellfish, tree pollen, and pet dander, but can really come from any source.
Signs and Symptoms
Common signs and symptoms are local swelling, redness, and itching on the surface of the skin or in the mucous membranes. Patients may also exhibit sneezing or tearing up.
Red Flags
Red flags are when the reaction moves beyond the local area of contact and starts affecting other systems. If the patient starts developing hives, or gastric, or respiratory distress, you should consider these to be red flags and get the patient moving to higher care.
Treatment
Remove contact with the allergens if possible and treat with an over the counter antihistamine (Benadryl, etc.)