On latest update no relevant published data on breastfeeding were found. Side effects and toxicity have not been tested, therefore its use would be preferably avoided or as much use it infrequently. Topical use is compatible with breastfeeding whenever it not used on the nipple. Stems of horsetail are used. It contains mineral salts (Sílicium, Potassium), flavonoids and steroids. Unproven effects are: diuretic, wound healing for burning injuries. Prolonged or abusive use may produce gastritis, vomiting, sea-sickness or stupor. May be confused with Equisetum palustre which is toxic due to that it contains Thiaminase and be cause of severe Vitamin B1 deficiency. A case possibly related to the appearance of Autism after the prolonged use in pregnancy has been described.