How does genetic predisposition cause hair loss?
In genetic predisposition the hair follicles become sensitive to hormones and gradually shrink, producing finer and shorter hairs. The process is slow and appears as regional thinning.
This type is common in men and women, and a similar family history is a clue. Loss is more marked in certain areas, such as the temples, crown or around the parting, than all over the scalp.
Diagnosis is mostly based on examination findings. Details are on the male and female pattern pages.
How do stress, illness and childbirth affect hair?
Intense stress, a febrile infection, surgery, childbirth or rapid weight loss can push part of the hair into an early resting phase, and diffuse shedding may appear roughly two to three months later.
This is called telogen effluvium. Because shedding begins months after the trigger, people often cannot link the two. Hair usually recovers once the trigger is gone, although this can take months.
See the dedicated page for more information.
Can iron, vitamin and thyroid problems cause hair loss?
Yes, some deficiencies and illnesses can contribute to shedding. Thyroid disorders, marked iron deficiency and inadequate nutrition are among them.
But it is not right to attribute every case of hair loss to a deficiency; supplements do not stop loss in someone whose blood values are normal. The doctor decides which tests are needed based on history and examination.
Crash diets, irregular eating and low protein intake can also affect the hair cycle.
Which medicines and illnesses can cause hair loss?
Some chemotherapy drugs, anticoagulants, some hormonal medicines and other drug groups can cause shedding. Autoimmune diseases and scalp infections can too.
If you suspect a medicine is causing loss, do not stop it on your own; talk to your doctor. In autoimmune conditions such as alopecia areata, round patchy loss appears and specialist assessment is needed.
If there is redness, scaling, pain or scarring loss on the scalp, dermatology assessment without delay is advised.
Which tests may the doctor request?
Tests vary from person to person. Commonly requested ones include a full blood count, iron and ferritin, thyroid tests and vitamin D; further tests may be requested if there are hormonal signs.
The same panel is not routinely requested for everyone. The scalp is examined, dermoscopy is done if needed, and a biopsy is rarely required.
Results are interpreted together; a borderline value does not always need treatment.
Frequently asked questions
Does stress cause hair loss?
Intense or prolonged stress can trigger temporary diffuse shedding. It usually starts a few months after the trigger and recovers over time.
Is a blood test needed for every case of hair loss?
Not always. The doctor decides based on history and examination; tests are requested more often in diffuse loss or when a systemic illness is suspected.
Which medicines cause hair loss?
Many drug groups can have this effect. Do not stop a medicine on your own; ask your doctor.
Is hair loss hereditary?
Genetic predisposition is a common cause, but not every case is inherited. Family history is a helpful clue in diagnosis.
Can hair dye or shampoo cause hair loss?
They can cause breakage of the hair shaft, but most shedding comes from the root. If there is an allergic or irritant reaction, a scalp examination is needed.
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This content is for general information and does not replace a personal medical assessment.