First, one must be familiar with the physiological characteristics of human hair growth
There are 3 types of human hair follicles: asexual, hermaphroditic, and male follicles. Asexual hair follicles are hair follicles that do not depend on steroid hormones for growth and are located on the eyelashes, eyebrows, occiput, forearms and lower legs. Hermaphroditic hair follicles are dependent on estrogen levels and are located in the lower part of the pubic triangle, the armpits and other parts of the body. Male hair follicles, on the other hand, require the presence of androgens and are located in the whiskers, ears, nostrils, pubic bone and frontoparietal area. Hair growth is a cyclic and repetitive process of asynchronous regeneration of hair follicles. Fang Hongyuan, Department of Dermatology, Affiliated Hospital of Armed Police Logistics College
The growth cycle of human hair follicles can be divided into 3 phases: anagen phase, degenerative phase and resting phase. The hair that falls off when combing or shampooing is mostly hair in the resting phase. Different parts of the hair have different growth cycles, and the hair of the same part also grows and falls out non-synchronously. Hair growth cycle is regulated by a variety of factors inside and outside the body, including the influence of neurological, endocrine, systemic nutritional status, environmental factors, etc.
Hair: the total average number of about 100,000, the fastest growth period in 15-30 years old, the average growth rate of 0.35mm / day, that is, l cm per month. general hair growth period of 2 to 8 years, the resting period of 1-4 months. The average daily hair loss is 25-100 hairs; the ratio of growth period to resting period hair is about 90:10. The growth rate of male hair is faster than that of female. Hair diameter and morphology varies with race and hair type. Different parts of the head of the hair its growth rate also varies.
Second, to identify whether it is hair damage or hair loss.
Humidity, friction, sunlight, heating, blowing wind, chemicals in swimming pool water, salts in seawater, etc. can cause damage to hair microdermis, blunt scissors haircut, razor cut, reverse combing, chemical perming or dyeing, bleaching, etc. can lead to hair damage. The main manifestation of hair damage is hair loss, therefore, the identification of hair damage or hair loss is the first step in the clinical diagnosis of hair loss.
The main clinical manifestations of hair damage.
① hair stem breakage: manifested as hair loss, in fact, hair breakage.
②Nodular brittle hair: the broken end is like a disconnected straw rope spread, this damage needs to stop external factors 2 to 4 years to return to normal.
③ hair tangles and bird’s nest hair: hair tangles when it is not easy to comb, so those with long hair in the cleaning, should be rubbed step by step along the root to the tip of the hair. In the case of bird’s nest hair, there is no other way to deal with it except to cut off all the hair masses and wait for the hair to grow out again.
Third, clarify the type of hair loss.
Whether the hair loss is diffuse or focal, and whether the hair loss is accompanied by scar formation. Focal alopecia includes single or multiple foci or more extensive focal alopecia. In male patients with androgenetic alopecia, for example, hair loss is often confined to the top of the head. Focal alopecia can also present as unifocal or multifocal alopecia. Although some types of “focal” alopecia (such as baldness) can be quite widespread, they are not likely to be typically “diffuse”. In focal alopecia, with the exception of androgenetic alopecia, characteristic short or broken hair can usually be found.
The presence of scar formation in alopecia areata reveals whether the hair follicle is permanently destroyed or whether hair growth is temporarily stopped. In patients with scarring alopecia, the hair bulb and sebaceous glands are violated and the skin on the surface of the follicle is relatively smooth and poreless as seen by the naked eye. However, it is sometimes difficult to identify scarring alopecia clinically with the naked eye alone, and a tissue biopsy is necessary to determine whether scarring is present.
Causes of non-scarring alopecia: mainly seen in the following conditions.
(1) Androgenic alopecia.
(2) Non-scarring alopecia associated with hereditary syndromes.
(3) Alopecia areata.
(4) Non-scarring alopecia associated with systemic diseases or other conditions such as resting alopecia, nutritional deficiency or metabolic deficiency states, endocrine disorders, drug or chemical effects, syphilis, etc.
(5) Traumatic non-scarring alopecia, such as hair pulling mania, traction alopecia (seen in hair styling, curly hair) or other causes, etc.
Fourth, introduce several common hair loss
1. Androgenetic alopecia (“seborrheic alopecia”).
Patients have more social problems than those with other skin conditions. Androgenetic baldness in men may indicate cardiovascular disease. Baldness in the frontal area, especially temporal and top hairline recession, is often manifested in female patients as a form of central baldness of varying severity, and more attention should be paid to its endocrine aspects. The ratio of growth phase to resting hair is significantly reduced. Most hairs do not exceed 8 cm in length, indicating that a shortened anagen phase is characteristic of this type of baldness.
2.Patch baldness.
It is a kind of limited patchy alopecia that can occur suddenly on any hairy part of the body. According to the clinical manifestations of patchy baldness, it can be divided into 8 types: unifocal patchy baldness, multifocal patchy baldness, total baldness, general baldness, diffuse patchy baldness, reticular baldness, serpentine baldness (or runner baldness) and horseshoe-shaped baldness.
The determination of the clinical type of baldness is important in determining the prognosis and determining the etiology. Limited baldness has a good prognosis, reticular baldness often suggests the presence of immune or endocrine abnormalities, and a significant proportion of patients may progress to total baldness, and serpiginous baldness is often combined with atopic physiology and has a poor prognosis. The prognosis is even worse in combination with cervical macular nevus.
It has also been classified into four types.
Type 1. Unusual type: It occurs mostly in people aged 20 to 40 years, with a duration of <3 years. Individual baldness often regenerates hair in <6 months, and total baldness can occur in 6% of patients;
2. Genetic allergic type: It usually develops in childhood, the course of the disease is >10 years, individual baldness often lasts for 1 year, and total baldness can occur in 75% of patients.
3. Pre-hypertension type: It mainly occurs in young people, with a rapid course, and 39% of patients have total baldness.
4. Type mixed type: Mostly occurs in people >40 years old, with a delayed course, and only 10% of total baldness occurs.
3. Diffuse alopecia.
(1) Hormonal: such as hair loss caused by hypothyroidism or hyperfunction, pregnancy or postpartum alopecia, androgenic baldness, degenerative or senile alopecia, oral contraceptives, etc.
(2) Nutritional causes: strict dietary restriction during weight loss can cause diffuse hair loss within 1 to 6 months, protein-energy malnutrition, essential fatty acid deficiency such as 2 to 4 months after inadequate fatty acid intake, iron deficiency, zinc deficiency, and biotin deficiency.
(3) Physiological stress: For example, biopsy specimens from patients with hair loss after fever show an increase in the number of normal resting hair follicles, resting hair loss may be a precursor to the onset of some systemic diseases, and surgery and trauma can also lead to stress alopecia.
(4) Drugs: Many drugs can cause resting hair loss and diffuse alopecia.
(5) Other such as toxins, radiation, liver and kidney insufficiency, syphilis, and especially limited skin disease can cause diffuse hair loss. A small number of difficult to find the cause can be called idiopathic alopecia.