Bronchospasm or a bronchial spasm is a sudden constriction of the muscles in the walls of the bronchioles. It is caused by the release (degranulation) of substances from mast cells or basophils under the influence of anaphylatoxins. It causes difficulty in breathing which ranges from mild to severe.Bronchospasms occur in asthma, chronic bronchitis and anaphylaxis. Bronchospasms are a possible side effect of some drugs: pilocarpine, beta blockers (used to treat hypertension), a paradoxical result