It is known that hormonal imbalance affect’s hypcrsensitivity. It has also been shown1 that the uterine tissues of mice in estrus were significantly morc sensitive to small amounts of serotonin and acetylcholine in Schultz-Dale tcsts than t,he uteri of mice not in estrus. Suppression of immediate skin tests has been obscrvcd while the known reactor was under hypnosis.2 Antihistamines,” aminophylline,4 and the sympathicomimetic drugs5 such as epinephrine, ephedrine and isoproterenol havc been shown to suppress immediate skin reactions for various allergens, but ACTH and cortisone in therapeutic doses do not significantly altcr these reactions.6 Antihistamines are especially effective in inhibiting reactions, as is aminophyllinc, but to a lesser extent. FeinbergT rcc~ciit~ly reported a tranquillizer which diminishes skin reaction in monkeys. If the full benefits are to be expected from skin tests, all unfavorable infliicnccs upon them must be eliminated. It is known that skin tests may bccome negative during, or immediately after, a severe allergic attack, and c.l(vation in temperature also reduces the reaction. The airn of this papcr is to investigate the influencc of menstruation on skin reaction in allcrgic people.