I don't know, you tell me.

Sexually induced sneezing or sex sneeze is a phenomenon characterized by sneezing during orgasm or sexual arousal.

Signs and symptoms
The person experiences sneezing as a result of sexual thoughts, arousal, intercourse, or orgasm.
Sneezing occurs independent of external nasal stimuli or allergens, and may occur at any point during a sexual experience. Both men and women are affected by the phenomenon.[1]

Causes
Mahmood Bhutta, an otorhinolaryngologist at John Radcliffe Hospital, states that sexually induced sneezing may be genetically determined, and may result from the way the central nervous system is wired: "This reflex demonstrates evolutionary relics in the wiring of a part of the nervous system called the autonomic nervous system. ... This is the part beyond our control, and which controls things like our heart rate and the amount of light let in by our pupils. ... Sometimes the signals in this system get crossed, and I think this may be why some people sneeze when they think about sex.[2]

Another possible explanation concerns the existence of erectile tissue in the nose, which may become engorged during sexual arousal, triggering a sneeze. Cranial nerve zero (autonomic) is also located in the nasal cavity. Its purpose is unknown, but it is thought to play a role (or used to play a role) in detecting pheromones.[1]

[en.wikipedia.org]