When does prophylaxis for hereditary angioedema become necessary?

It depends: Great question. It really depends on two factors: 1. The severity of the reactions, and 2. The frequency of the reactions. When the reactions become too severe and/or too frequent, prophylactic treatment is recommended. Now, what does too severe/frequent mean? It depends on the person. Ultimately, when the reactions impact a patient's daily life, it's time to consider prophylaxis.

HAE prophylaxis: Some of the recent recommendations suggest prophylaxis if patients have more than 1 attack per month. If symptoms are more significant- such as throat or laryngeal swelling or abdominal pain/obstruction or swelling, then it is wise to consider prophylaxis with even fewer attacks. Suggest you see allergist with expertise in hae.