Be wary of Mutli-Level Marketing promotions of "challenges." Recently there have been some for hair and nail growth. One of the claims are that it can make your hair grow longer (1-4"/month). You hair growth rate is usually determined by your genetics and can range from 0.5-2 inches per month. That rate can be reduced by a poor diet, stress and other factors.
These challenges usually involve the taking of supplement that contain keratin and biotin and other ingredients.
Biotin: The pills can have a Biotin dosage of 5000mcg. The daily recommended intake of 30-100mcg. This is unnecessary mega-dosing as a lack of biotin in the body is rare. You should not be taking any pill or supplement like this without a consultation with a family physician.
Keratin: Hair loss has actually been noted with ingestion of liquid keratin products. It may be possible to have too much keratin causing rough, dry skin and course hair. Since keratin is a protein, too much of it can cause the kidneys to work harder to excrete it in the urine called proteinuria and can lead to renal insufficiency. Again, do not take supplements/pills without consulting a family physician.
MSM: Has shown some, but limited positive results for treating allergies, repetitive stress injuries, certain bladder disorders like interstitial cystitis, wounds and arthritic knee pain. It can have side effects if taken orally such as diarrhea or gastrointestinal discomfort. Why this is in a hair product, I'm not sure. I can only assume that they may be trying to link it to hair retention somehow.
The disclaimers also state that certain statements have not been evaluated by the FDA. Also on one site, there is small print about the testimonials stating "are purely cosmetic in nature and do not claim to cure/treat/prevent any skin & hair related disorders. "
The cost of one such product is $55 for 60 pills. You can find other products in the hair/nail section of a drugstore with similar ingredients for much less if you are so inclined to want to go this route.
My advice would to stay clear of these mlm products. They often use shady selling techniques to get you buy into the whole system, let alone the products. They use testimonials as scientific proof of it actually working is slim to non-existent. The testimonials are usually swimming in biases and credulity.