What severe allergic reaction can occur from Benzylpenicillin?

Benzylpenicillin, a type of penicillin antibiotic, can trigger a severe allergic reaction known as angio-oedema. This reaction is characterized by swelling of the deeper layers of the skin, often around the eyes and lips, and sometimes in the throat, which can lead to serious complications such as airway obstruction. This allergic response is due to the body's immune system mistakenly identifying the medication as a harmful substance, prompting the release of histamines and other chemicals that cause these symptoms.

The other options do not represent typical severe allergic reactions associated with Benzylpenicillin. Respiratory infections are unrelated as they are not a direct reaction to the drug but rather a potential condition for which antibiotics may be prescribed. Dehydration does not directly result from an allergic response, and while it may occur in various illnesses or situations, it is not a specific reaction linked to Benzylpenicillin. A bleeding disorder is also not associated with allergic reactions to this medication; it generally involves other underlying conditions or medications that affect coagulation.

Thus, angio-oedema is the correct and specific response to consider when discussing severe allergic reactions related to Benzylpenicillin use.