There are pheromones released when we're sexually excited.
I don't think there are pheromones for when you've gone without sex. However, your general horniness is higher than normal and there will be clues in body language others can pick up on. In one of her books, Erica Jong (famous for Fear of Flying and the zipless fuck) says how strangers could tell when she wanted sex and they'd even start following her on the street.