Predisposing factors for anaphylaxis

It is clearly established now that pre-existing asthma may exacerbate or predispose to anaphylaxis. This is clearly in keeping with the concept of the target organ of the reaction being important. Sampson's group of fatal and nonfatal reactors were clearly distinguished by the presence of a diagnosis of asthma, particularly if the asthma was poorly controlled. Our study in Southampton has supported this finding (Table 4.4).10,21

Other factors that may predispose to severe disease are the use of medications that may interfere with the normal physiological response to an allergen, i.e. the epinephrine (formerly adrenaline) response. The typical drugs implicated are the cardiac drugs called angiotensin converting enzyme (ACE) inhibitors which inhibit the physiological angiotensin reaction to hypertension, and the more familiar beta blockers prescribed for ischaemic heart disease. The latter may inhibit the generation of a faster heartbeat to maintain organ profusion in the face of allergen-mediated fall in blood pressure.

Alcohol is a clear example of a drug that may work in several ways. In amounts that are consumed socially, it impairs judgement and encourages risk taking and may therefore impair the intellectual response to being exposed to a food known to potentially contain an allergen that is unsafe for the subject (the classic example being the Indian takeaway). Alcohol also works physiologically by causing relaxation of blood vessels, leading to a fall in blood pressure. A fall in blood pressure may be more precipitous if an allergen is consumed during a meal in which alcohol is also consumed.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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