Smegma
Smegmais a white substance formed from a combination of dead cells, skin oils, moisture and naturally occurringbacteria, that forms in mammalian genitalia. In females it collects around the clitoris and labial folds.
Aliphatic acids
Approximately one third of women producealiphaticacids. These acids are a pungent class of chemicals which otherprimatespecies produce as sexual-olfactory signals. While there is some debate, researchers often refer to them as humanpheromones. These acids are produced by natural bacteria resident on the skin. The acid content varies with the menstrual, rising from one day aftermenstruation, and peaking mid-cycle, just before ovulation.
Sexual arousal
Main article:Human sexual response cycle
Sexual arousalresults in a number of physical changes in the vulva. Arousal may be broken up into four somewhat arbitrary phases: Excitement, Plateau, Orgasm, and Resolution.
In the left image female genitalia are in the resting state. In the right image the female is sexually aroused, the vulva is moist and the labia are slightly swollen.
Excitement
Vaginal lubricationbegins first. This is caused byvasocongestionof the vaginal walls. Increased blood pooling there causes moisture to seep from the walls. These droplets collect together and flow out of the vagina, moistening the vulva. The labia majora flatten and spread apart, and the clitoris and labia Minora increase in size.
Unlike an average man, whose sexual excitement will cause an obviouserection, a woman experiencing arousal may not be aware that her vagina has producedlubricationand has been engorged with blood.