Keratin is the tough, fibrous protein that forms the structural backbone of your hair, nails, and skin's outer surface. Because raw keratin is not digestible, supplement manufacturers use a process called hydrolysis to break it into smaller peptides that the body can actually absorb and put to use. Once absorbed, these peptides give your body the building blocks it needs to repair and reinforce keratin-based tissues.

When you take hydrolyzed keratin orally, the peptides are absorbed through the gut and delivered via the bloodstream to hair follicles, nail beds, and skin. There, they provide amino acids — especially cysteine — that are the raw material your body uses to synthesize new keratin. Cysteine is critical because it forms the disulfide bonds that give keratin its strength and resilience. Supplementing these peptides essentially tops up the supply your body needs to produce stronger, thicker hair and nails.

Oral capsules and powders deliver keratin systemically for hair, nail, and skin support from the inside out. Topical keratin products (shampoos, treatments) coat the hair shaft to temporarily smooth and protect but do not penetrate the follicle or alter growth biology. Salon keratin treatments work similarly — they bond to the hair surface using formaldehyde or safer alternatives but are cosmetic rather than therapeutic.

• Hair thinning and shedding
• Brittle or weak nails
• Dull, damaged, or frizzy hair
• Slow nail growth
• Dry or rough skin texture
• Hair breakage and split ends
• Weak hair after chemical or heat damage
• Skin elasticity and firmness

• Progressive nail brittleness in individuals with low dietary protein intake
• Hair shaft damage from ongoing heat or chemical exposure (when used concurrently)

Keratin itself is not found in food — dietary proteins are broken down into amino acids before absorption, and no food delivers pre-formed keratin peptides. However, eating protein-rich foods high in cysteine and sulfur-containing amino acids gives your body the raw materials to synthesize its own keratin. Top supportive foods include: (1) Eggs — especially egg whites, which are one of the richest sources of cysteine; (2) Lean poultry like chicken and turkey, which supply complete protein with good sulfur amino acid content; (3) Beef and lamb, which provide both cysteine and methionine needed for keratin synthesis; (4) Legumes such as lentils and black beans, which offer plant-based protein and sulfur compounds; (5) Sunflower seeds and pumpkin seeds, which are concentrated sources of cysteine-rich protein. Ensuring adequate overall protein intake (at least 0.8g per kg of body weight) is the most important dietary step to support keratin production naturally.

• Mild nausea or stomach discomfort at higher doses
• Bloating or gas, especially when starting supplementation
• Rare allergic reactions in individuals sensitive to wool or poultry proteins (source-dependent)
• Topical salon keratin treatments carry separate concerns — formaldehyde-based products can cause eye, nose, and throat irritation with repeated professional exposure

• Recommended daily: 500 mg to 1,000 mg of hydrolyzed keratin per day (clinical trials typically use 500 mg of Cynatine HNS daily)
• Best time of day: No strict timing requirement — morning or midday works well for most people
• With or without food: Take with food to improve tolerability and support amino acid absorption alongside dietary protein
• Time to effect: 4 weeks for early changes in shedding; 8 to 12 weeks for visible hair, nail, and skin improvement
• How long to take it: Best results come from consistent daily use for at least 90 days. Long-term supplementation is generally safe; benefits may diminish if discontinued, as the body's keratin synthesis returns to its baseline rate.