Our hair doesn’t grow continuously. Every follicle cycles through distinct phases that determine when hair growth comes through, rests, or is shed. Understanding these phases is the first step to grasping why hair thins, and what might help it regrow.
The Biology of the Hair Cycle
Hair on the scalp grows in a repeated cycle made up of four main phases: Anagen phase (growth), Catagen phase (transition), Telogen phase (resting), and Exogen phase (shedding).
• Anagen is the active growth phase. During this time, cells at the base of the hair follicle divide rapidly, forming new hair strands. On the scalp, the anagen phase can last between two and seven years, which is why hair can reach considerable length if undisturbed.
• Catagen, a brief transitional phase, lasts around two to three weeks. The follicle shrinks, and hair production slows down before entering rest.
• Telogen is a resting period; hair growth halts and the old hair remains until it is eventually shed during the exogen phase. On a healthy scalp, about 10–15% of hairs may be in telogen at any one time.
Stimulating the Anagen Phase Naturally
Emerging evidence suggests certain plant-based compounds may help “wake up” dormant follicles, restarting or prolonging the anagen growth phase. One of the most promising of these is the extract from pea sprouts (Pisum sativum), often formulated in topical treatments. A 2025 study found that pea sprout extract promotes follicle regeneration by prolonging the anagen phase and modulating oxidative and inflammatory signalling.
By encouraging follicles to re-enter growth mode sooner, these compounds may help restore hair density over time, rather than merely masking thinning. This offers hope for those experiencing hair thinning due to follicles entering a prolonged resting period.
Distinguishing Hair Density from Thickness
It’s important to differentiate between “more hair” (density) and “thicker hair” (diameter). A good hair growth serum typically works on both fronts by biologically stimulating follicles for new hair while cosmetically supporting existing strands.
Biological ingredients (like pea sprout extract, biotin, zinc, etc.) nourish follicles and promote new growth, while many serums or elixirs add a coating of keratin or other agents that increase strand diameter for a fuller look in the interim. For someone starting treatment, this dual effect means visible improvement sooner, and real long-term growth if they stay consistent.
Inside-Out vs Outside-In: Why Nutrition Matters Too
Topical treatments offer benefits but they’re only part of the equation. Follicles need raw materials (proteins, vitamins, minerals) and overall healthy physiology to build new hair. If your diet is poor, or you’re lacking key nutrients, a serum alone won’t accomplish much.
That’s why experts recommend combining external care with internal support: a balanced diet rich in protein and micronutrients, good sleep, stress management, and healthy lifestyle habits. Together, these create optimal conditions for follicles to respond to stimulation and stay in growth cycle.
Managing Expectations: Results Need Time
Of course, hair growth is a slow biological process; no product delivers instant transformation. Because of the length of the anagen-telogen cycles, noticeable results from a hair growth serum or elixir typically take months of consistent use.
It’s important to view treatment as a long-term commitment rather than a quick fix. With patience, combined care (topical + nutrition), and realistic expectations, you may gradually restore fullness and slow thinning, but overnight miracles are never going to happen.
