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How can I recognize a reaction?
Each allergic individual will react in a specific way (i.e. with specific symptoms). This tends to be consistent from reaction to reaction unless the mode of contact is altered (i.e. ingestion, injection, inhalation). The severity of reaction, however, is less predictable. The quantity of allergen (trigger), asthma, the use of beta-blockers (cardiovascular medication) can affect it and this is why strict avoidance and the immediate use of epinephrine are imperative. You should discuss your/your child's particular signs and symptoms with your allergist and make sure that caregivers are aware of these. Many people watch for hives to develop, but these may not be present.
Signs and symptoms can include:
Mild Symptoms
- tingling, numbness, pain in the lips and tongue;
- itchy eyes, nose, face;
- flushing of the face and body;
Moderate to Severe Symptoms
- swelling of the eyes, face, lips, tongue and throat;
- difficulty swallowing;
- hives;
- abdominal cramps, vomiting, diarrhea;
- wheezing, coughing, difficulty talking and breathing;
- a sense of foreboding, fear and apprehension;
- weakness and dizziness;
- drop in blood pressure, loss of consciousness, death.
Most serious reactions occur rapidly and respond quickly to epinephrine. Some life-threatening reactions may have a delayed onset or recur several hours after seemingly effective treatment. This is why it is imperative that people remain in hospital for 3-4 hours following a mild reaction and longer following moderate to severe reactions (Sampson). Most biphasic reactions recur up to 8-12 hours later, but some have been seen 25 hours later. The initial symptoms may also be masked or muted if the patient has been taking steroids or antihistamines.
What happens during a reaction?
An allergic individual produces antibodies (IgE) which recognize specific proteins (allergens). These antibodies are present on the outside of mast cells and basophils. When an allergen couples with the IgE antibodies, histamine and other mediators of anaphylaxis are released from the mast cells and basophils. These mediators cause blood vessels to leak (which leads to swelling and drop in blood pressure) and airways to narrow (wheezing). Antihistamines cannot reverse all the effects of these mediators and their onset of action is too slow. Epinephrine, however, counters all the sequelae of anaphylaxis and must be given at the earliest sign. Mast cells and basophils can also release mediators via direct stimulation. This can occur with certain drugs (morphine) and exercise.
Do reactions worsen with each exposure to allergen?
The severity of a reaction reflects a person's allergic sensitivity at the time of the event and the allergen load (quantity of triggering agent). Both of these can be extremely variable. Hence, ensuing reactions may be consistent, more severe or less severe. People who have had very mild reactions may suffer a severe reaction and vice versa. It is imperative to err on the side of caution and be prepared for a severe reaction at any time.
Are some people more at risk of having a severe reaction?
Through an examination of fatal and near fatal allergic reactions, Dr. Hugh Sampson and others have noted a few risk factors for severe anaphylaxis. These include asthma, previous severe reaction, allergy to particular allergens (peanut, tree nut, seafood, fish) and concurrent medication with beta-blockers (these block the therapeutic effects of epinephrine). (Sampson, H.A. Metcalfe et al. Fatal and Near-Fatal Anaphylactic Reactions to Food in Children and Adolescents. New England Journal of Medicine, 327:380-84,1992)
When is my child most at risk of an anaphylactic reaction?
Your child is likely at higher risk when under the care of other people. In Dr. Hugh Sampson's study, 4 out of 6 fatal reactions occurred outside of the home. (Sampson, H.A. Metcalfe et al. Fatal and Near-Fatal Anaphylactic Reactions to Food in Children and Adolescents. New England Journal of Medicine, 327:380-84,1992) Teen-agers and young adults are also at increased risk because they are more likely to tempt fate and take chances.
I think that my child had an anaphylactic reaction, but we gave the epinephrine quickly and symptoms abated. Are there any tests to indicate whether or not this was a reaction?
If you are unsure about a reaction, there are two tests that can be done after the fact to answer this question. You need to check this with the physician in the emergency room. Methylhistamine is a breakdown product of histamine and can be found in the urine after a reaction and mast cell tryptase can be found in the blood.
Last date modified on Friday, December 20, 2002
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