"I've been taking RhusTox annually (in Iowa from about March thru October) for years. It is obvious to me, after several exposures to Poison Ivy, that this product (previously RhusTox, now Outdoor Joe's) is effective in building immunity to the reactions. It won't make you immune, but it significantly reduces the reaction to such an extent that doctor-administered steroids or another medical treatment is no longer needed. I can't imagine why anyone that enjoys the outdoors, hiking or gardening, wouldn't use this preventative measure."