According to a number of mainstream herbal texts and studies. Side effects like gastrointestinal upset, diarrhea and increased blood pressure are rare but possible. Additionally, I would have concerns about recommending this herb for a teen due to its ability to interfere with the body's use of sex hormones like testosterone and estrogen.
In addition to these comments I would like to add that in addition to low thyroid, I have seen cases where someone simply had a dairy intolerance. They could digest if fine but had cystic acne and sometimes a lot of phlegm in their system. I have seen cases where someone quit dairy for a couple of weeks and saw a HUGE improvement. No kidding- they called it a miracle. Forget the acutane, as well as the saw palmetto. There is a reason your body is responding with this problem and you are only shoving the symptons down while not addressing the underlying cause.
In addition to stopping dairy I would suggest trying a far infrared sauna on a regular basis. In a good one you will sweat a ton and yet not heat the skin too much but, also, if you cannot find a far infrared one, just use a hot steamroom. That will help detoxify your skin. water water water, also aim to have a less acidic system (there are books about pH levels). Bread products create oily skin in some people, you can always do an elimination diet -which is when you stop eating certain foods for a period and see how you feel- and if the skin becomes better, then you know you are slightly allergic to that food.
The most recent information learned in naturopathic school is that saw palmetto works for prostate problems by acting as an anti-inflammatory, and not by reducing the conversion of testosterone to DHT. (I know 99% of sources will say otherwise). I'm not sure which is correct, but if the herb reduces DHT or not, it may not be the best way to try to treat acne.
Some basics are to go over the diet, less sugar, less garbage fats. Consider digestion. Eat good foods, eat slower, chew, don't wash down food with soda. Digestive enzymes may help, and also zinc deficiency can lead to acne. The body needs zinc to convert vitamin A to it's active form. You can buy zinc as a liquid and if it tastes like water then you know you need zinc, so there is no guesswork. Vitamin A supplementation is also a consideration, but it's not something to take indefinitely.
Also look for major allergens like dairy, wheat, corn, soy and eggs. Those are the basics I would think of first before trying something like saw palmetto. Also a high stress lifestyle is bad for acne and hormonal balance.
Saw Palmetto is used in some countries as an aphrodisiac because it contains a chemical which blocks the Re-uptake of 5-DHT, the chemical which causes penile erections to go down after orgasm. Also, it keeps your hair follicles from shrinking thereby crushing the hair, which breaks off; soon thereafter your hair follicle closes, if that is your geneaology.
