Common misconception: shaving causes hair to grow back thicker and at a faster rate

Contrary to a widely held belief, shaving does not alter hair density, thickness, or growth rate. This illusion arises from a purely visual and tactile phenomenon. When one shaves a hair, it is cut at the skin’s surface, at the level of the hair shaft. The hair is then severed cleanly, giving it a blunt, rigid end, unlike a natural hair whose tip is tapered. This can make it feel sharper to the touch, more visible, and give it a thicker appearance. It may also appear darker because the freshly cut hair has not yet been exposed to light or external agents that slightly lighten it over time. Finally, the simultaneous regrowth of multiple hairs cut at the same moment can create an impression of increased density.

The study conducted by Aliakbarpour et al. (2017), published in the Journal of Cosmetic Dermatology, aimed to determine whether the act of shaving hair could influence their growth, thickness, or density compared with a scissors cut. This issue arises especially in the context of preparing for laser hair removal in women with hirsutism, a disorder characterized by excessive hair growth in areas normally sparsely haired in women, due to androgen excess.

To answer this question, the researchers conducted a randomized clinical trial involving 60 women with hirsutism (defined as the appearance of hair in so-called masculine areas, which are normally hairless in women). Participants were assigned to two groups: one group was instructed to shave the treatment areas, while the other simply trimmed the hair with scissors before beginning laser sessions. The study lasted 12 weeks, with regular patient follow-up and objective assessment of hair regrowth. The researchers evaluated several parameters: hair density, hair thickness, regrowth rate, and the efficacy of the laser treatment according to the preparation method used. The results showed that no significant difference was observed between the two groups in terms of regrowth rate or hair thickness. In other words, shaving did not make the hairs thicker or more numerous. Moreover, the efficacy of the laser treatment was not affected by the chosen pre-treatment grooming method. This study therefore confirms that shaving, contrary to a persistent misconception, does not alter hair quality or the growth cycle, even in a hormonal context such as hirsutism. This reinforces existing literature indicating that any perceived thickening of hair after shaving is merely illusory.

Human hair growth is regulated by complex biological mechanisms that act primarily at the hair follicle, a structure located in the dermis. This follicle follows a hair cycle consisting of several successive phases. The longest phase is the anagen phase, or growth phase, which lasts from 2 to 7 years. During this period, cells divide rapidly at the base of the hair, while matrix cells migrate outward to form the hair shaft. Next comes the catagen phase, a short transitional phase of about three weeks, during which the follicle undergoes involution: the hair loses its connection with the papilla and retracts. The telogen phase, or resting phase, follows for about three months; it is a period of near-zero cellular proliferation, with the papilla retracting toward an area near the bulge, without significant apoptosis. Finally, there is a distinct phase called exogen, corresponding to the shedding of the old hair while a new hair continues to grow. Each follicle follows this cycle independently, under the control of numerous internal factors, with a central role played by hormones.

Among these hormones are the androgens, particularly testosterone and its active form, dihydrotestosterone (DHT), which are key determinants of hair density, thickness, and distribution. They trigger the conversion of fine, lightly pigmented hairs into thicker, longer, and darker ones, especially during puberty. These effects are amplified under hormonal imbalances, as observed in certain pathological conditions.

Age is also a major factor: body hair develops during adolescence, stabilizes in adulthood, and then evolves with aging. In women, the menopause can be accompanied by thinning of certain hairs and the emergence of thicker hairs in other areas due to hormonal changes. In men, areas such as the scalp may lose density while other areas become hairier. The genetics plays a crucial role as well: each individual inherits a specific hair program that determines hair distribution, density, and texture. Thus, under identical habits, two people can exhibit very different levels of body hair.

Finally, certain medical disorders directly influence hair growth. This is notably the case with polycystic ovary syndrome (PCOS), which leads to an excess of androgens in women, or with certain endocrine diseases affecting the adrenal or thyroid glands. These pathological effects on hair follicles have been detailed in recent studies describing the hormonal regulation pathways of hair growth.

In short, human body hair results from a complex interplay of hormones, genetic background, age, and health status—far more than from a purely superficial act like shaving.

• Macwilliams P. & al. Shaving and hair growth. The Journal of Investigative Dermatology (1970).

• HATTORI M. & al. Regulation mechanisms of hair growth. Current Problems in Dermatology (1983).

• Androgens and hair growth. Dermatologic Therapy (2008).

• ALIAKBARPOUR F. & al. A randomized clinical trial on the comparison between hair shaving and snipping prior to laser hair removal sessions in women suffering from hirsutism. Journal of Cosmetic Dermatology (2017)

• MECZEKALSKI B. & al. Hormonal Effects on Hair Follicles. International Journal of Molecular Sciences (2020).

• ALADRAJ J. F. & al. Effects of Hormones and Endocrine Disorders on Hair Growth. Cureus (2022).