Guests at pheromone parties are asked to submit a slept-in T-shirt that will be smelled by other participants, who will pick a partner based on scent.

The parties started out as an experimental matchmaking fest by a California woman weary of online dating, a major newspaper reported.

Partygoers huddle around several tables covered with plastic freezer bags stuffed with shirts and an index card bearing a number at these events.

Once they find one they liked, a photographer snaps a picture of them holding the bag and project it onto a wall so the shirt’s rightful owner could step forward and meet his or her odour admirer.

The parties are a marked contrast to the proliferation of online dating sites, which demand countless details from singles, and in some ways are taking romance back to its most primal beginnings.