IMPORTANT CONSIDERATIONS ABOUT ALLERGIC REACTIONS
a. Effects of an Allergic Reaction. An allergic reaction has several effects on
the body. These effects occur mainly because of the large concentration of histamine
that is released. Peripheral vasodilatation occurs, and capillaries become more
permeable. Here, blood plasma "leaks" from the capillaries; the capillary blood volume
drops because peripheral vasodilatation and increased permeability of the capillaries.
Consequently, there is a decrease in blood pressure. Bronchoconstriction, which can
interfere greatly with breathing, may occur. The histamine release may also cause
severe rash or hives.
b. Types of Allergic Reactions. There are several types of allergic reactions.
One type of allergy is the mild local reaction to general antigens. These reactions are
not severe. The antigen producing the reaction can be anything from chicken egg white
to horse dander. Allergic rhinitis is an antigen antibody reaction with symptoms
occurring in the nasal mucosa. When the antigen is pollen, then it is called hay fever.
Hay fever is characterized by edema (swelling), sneezing, itching, and increased
mucous secretions. Asthma is characterized by bronchoconstriction as well as
wheezing, dyspnea, and coughing. The cause of asthma is frequently an allergic
reaction to airborne antigens (it may also be caused by non-allergy related factors).
Urticaria (or hives) is characterized by wheals (edema), erythema, and itching of the
skin. Foods, drugs, clothing, parasites, and many other substances may cause
c. Allergic Reactions from Drugs. Allergy can also involve mild local and
systemic drug hypersensitivity reactions. The drugs that commonly cause these
reactions include biologicals and antibiotics. Hives (urticaria) (swollen red areas on the
skin) and swollen eyelids and lips are outstanding features here. In addition, swelling
and pain that occur in joints and muscles when a patient is taking a drug, it is a possible
indication the patient is allergic to the drug. An elevated temperature is the third
indication that an allergic reaction may be occurring. The lymphatic hypersensitivity
reaction is swelling. The respiratory system reaction is bronchoconstriction, while the
nasal reaction is a runny nose. Jaundice is a symptom of the hepatic reaction, while
vasodilation and increased permeability of the blood vessels are the circulatory system
d. Systemic Reactions from Drugs. In addition, systemic reactions occur
whenever a drug or an antigen that reacts with abnormal anti-bodies is introduced into
the body. One type of systemic reaction is serum sickness. The signs and symptoms
of mild drug hypersensitivity and serum sickness may be identical. Serum sickness
occurs several days after an injection of a foreign protein, such as horse serum, into a
patient that is not already immune. Antibodies are not released into the tissues until 7
to 10 days later. After this period, the reaction between the newly formed antibodies
and the still present protein of the horse serum results in an allergic reaction throughout
the body. It is similar to anaphylaxis, except in serum sickness the reactions are slow in
occurring. The patient usually recovers without complications.