I'm amazed that for the sake of reducing one's symptoms, we don't consider what other symptoms can be brought on by ingredients that are synthetic, especially for those of us with allergies and weakened immune systems. Natural progesterone is the exact same hormone that is produced by a woman's ovaries. It's made from naturally occurring plant steroids found in the wild yam. It is NOT the synthetic version that is commonly purchased as tablets with a prescription such as Provera. The synthetic progesterone can produce severe side effects, including increased risk of cancer, abnormal menstrual flow, fluid retention, nausea, skin rashes, migraines and depression.
Side effects are extremely rare with natural progesterone.
The only side effect of concern is that it might slightly alter the timing of the menstrual cycle. I finally found a manufacturer that actually produces natural progesterone cream with absolutely no synthetics. You can actually pronounce all the ingredients - a rarity in personal care products. Many women report that progesterone creams either don't reduce their symptoms, make them worse, or bring on new symptoms of allergic reactions. It's no wonder, when you look at the majority of creams on the market and what they contain.