Certain physiological factors  such as the menstrual cycle are thought to modify acne.  Of female subjects, 60-70 per cent notice a deterioration of their acne in the week before menstruation, the lesions remaining more prominent for the next 7-10 days. There is, however, a remarkable lack of precise information regarding  the stage of the  menstrual  cycle at which acne becomes worse.  Nor is  there  much  data  available comparing severity of acne with menarche, duration and frequency of periods and hirsuties. Figure 2.8 shows no correlation between acne severity and hirsuties.  It has been suggested that one  characteristic of patients with premenstrual exacerbation of acne is menstrual disturbance in the form of irregular periods and premenstrual tension.8 However, this author has found that  85  per cent of females with acne have a frequency of menstruation which fits with the distribution of a normal population. It is not known if those females with irregular periods respond less well to conventional acne therapy than other groups. The effects of other hormonal variations on acne, for example that of pregnancy, are unclear. Some authors have found that acne improves during pregnancy,  whereas others have reported a deterioration.

  The contraceptive pill in its commonest combination, i.e. the  mini-pill (0.03 |xg ethinyloestradiol),  probably has a limited, if any, effect on acne but there is evidence that the maxi-pill,  containing larger  amounts  of oestrogen  (0.05 (xg, or  more, ethinyloestradiol) has  a considerably greater beneficial effect on acne lesions.