如何防止脱发以及重新生发，虽然从古代开始就有各种尝试，但至今并无真正的特效药。目前两类较常见的药物是外用 minoxidil 「米诺地尔」和口服 finasteride「非那雄胺」。
泰国 Mahidol University 2014年发表的论文（简介参见 NIH 官网）得出结论：男性脱发最佳药物为口服 finasteride 和外用 minoxidil；女性脱发的最佳药物是外用 minoxidil。原文为：“An assessment of the evidence quality of current publications indicates that oral finasteride (for men only) and topical minoxidil (for men and women) are the best treatments of AGA.” 这两类药物都是基于其他研究和用药中偶然发现的副作用。
1950 年代，Upjohn Company 测试用 minoxidil 治疗口腔溃疡，并没有成效，却发现它可以扩张血管；在接下来测试用于高血压的时候，又无意中发现它有促进毛发增长的副作用。经过更多测试后，Upjohn Company 遂将 minoxidil 研制为生发药物，并于1988年获得美国 FDA 批准用于治疗男性脱发和秃顶，这就是如今最常见的生发药物洛健 Rogaine。Upjohn Company 后被辉瑞公司收购，就是做伟哥的那家公司。
1991 年 Upjohn 据此推出了 Rogaine。1996年，FDA 批准将 minoxidil 作为 OTC 药物，无需处方即可购买。
- 1-month supply of Men's Rogaine 5% Minoxidil Foam hair growth treatment to help treat hair loss, maintain hair density and allow for the regrowth of fuller hair
- Formulated with 5% Minoxidil, our fast-working hair regrowth treatment works to boost hair follicle activity and hair protein production and is clinically proven to regrow up to 25% more hair
- Men's hair growth treatment also contains botanical extracts and emollient to help maintain a healthy, conditioned scalp, plus alphahydroxy acid (AHA) to promote natural skin exfoliation to help keep follicles open
- 4-month supply of Women's Rogaine 5% Minoxidil Foam hair growth treatment to help treat thinning hair, hair loss and regrow fuller hair
- Specially formulated for women, this fast-working hair growth treatment is made with 5% Minoxidil and is clinically proven to regrow up to 25% more hair and works to boost hair follicle activity and hair protein production
- Hair thinning treatment also contains botanical extracts and emollient to help maintain a healthy, conditioned scalp, plus alphahydroxy acid (AHA) to promote natural skin exfoliation to help keep hair follicles open
Finasteride 也称非那斯特莱，原本用于治疗前列腺肥大。皮肤中有些雄性荷尔蒙可导致脱发，而 finasteride 可以阻止这些雄性荷尔蒙的产生，从而防止或减轻脱发。
下面是美国卖得不错的「防脱发」洗护产品和「生发保健品」，很多顾客好评，说明有些人用过之后可能出现了改善，然而其效果并未经过 FDA 评估和批准，只能说因人而异。
- GREAT FOR THE SKIN AND HAIR: Rich in vitamins and fatty-acids, castor oil promotes better hair growth and helps nourish and hydrate the skin. 100% NATURAL AND ORGANIC: Produced with the highest quality standards using real castor oil, sourced directly from organic artisanal farmers in India
- SUITABLE FOR ALL HAIR AND SKIN TYPES: Made using organic, chemical-free substances, the Sky Organics Castor Oil is perfect for all skin and hair types. It is also free from artificial additives and won’t cause any allergies and irritations when used. Castor oil reduces stretch-marks and acne as well.
- COLD-PRESSED OIL: The Organic Castor Oil from Sky organics is cold-pressed without heat or chemical substances like hexane. This way, it retains all the healing properties of the oil, without any harmful additives or ingredients.
- BEST HAIR GROWTH BLEND – Packed with natural extracts, amino acids, Biotin, Keratin and Rosemary Oil, Vitamins B and E, Saw Palmetto and more, this shampoo features proprietary hair growth complexes clinically indicated to stimulate deep growth and prevent breakage and hair loss.*
- BREAKTHROUGH COMPLEXES – Amino Kera NPNF Keratin complex penetrates deep to strengthen and revitalize damaged hair while moisturizing and conditioning.* 3HC stimulates cells responsible for growing fibers and regulating hair follicle development.*
- DHT BLOCKER – Saw Palmetto and Green Tea are essential to preventing dihydrotestosterone (DHT) to promote regrowth of natural hair.* Additionally, Rosemary Oil helps treat alopecia and thinning hair.*
- BIOTIN FOR HAIR GROWTH this is a thickening shampoo for color treated hair damaged hair and oily scalp. Our natural shampoo has tea tree for dandruff and pure rosemary essential oil for hair growth.
- HAIR FOLLICLE STIMULATOR our hair growth shampoo is like a biotin supplement for your hair. It has essential oils for hair growth that help this cleanser to act as a DHT blocker shampoo for regrowth.
- NATURAL HAIR VOLUMIZER hair thinning can cause thick hair to look dull and thin hair to look flat. Our root lifting densifying shampoo leaves hair with more body and fullness as well as softness.
- TOP RATED 2019 SHAMPOO FOR HAIR REGROWTH STIMULATION
- Contains highly effective CaffinoPlex blend designed and researched to aid in healthy hair growth
- Contains powerful caffeine compounds which have been shown to reduce hair loss, stimulate hair growth and block effects of testosterone within the skin
- Contains solubilized Keratin Breakthrough Ingredient that Increases hair growth and thickness
- Contains a blend of over 23 essential vitamins required by hair to aid in circulation
- Promotes hair growth while decreasing hair loss
此类洗护产品的主要成分是 biotin 生物素和 keratin 角蛋白、蓖麻油和其他各种精油；而生发保健品的主要成分是各种维他命、生物素和锌、碘等矿物质，原因是某些脱发可能是由于营养不良引起，若你的脱发问题并不是因为缺乏维生素或矿物质，那么此类保健品的功效可能有限。
美国常见的「生发」洗发水（Hair Regrowth Shampoo）有 Maple Holistics 生物素洗发水、Ultrax Labs 咖啡因洗发水、PURA D’OR 增发洗发水、Pronexa 生发洗发水、Honeydew 抗脱发洗发水等。