Dry hair and disease: causes, syndromes, and warning signs

Summary

• Diseases that can cause dry hair
• Brittle hair caused by an underlying condition
• Care for dry hair and sensitive scalp
• Frequently asked questions

Dry hair can sometimes signal more than just a lack of moisture. This article examines the link between dry hair and an underlying disease, whether hormonal, deficiency-related, or systemic, and specifies which symptoms should lead to consulting a healthcare professional.

Diseases that can cause dry hair

Hair dryness is not always due to an external cause. It can be a sign of an internal imbalance: insufficient sebum production, open and porous cuticle, or poorly nourished follicle.

Thyroid and hormonal disorders

Among the most frequently documented medical causes of dry hair are thyroid disorders. Hypothyroidism slows down overall metabolism: the hair fiber directly suffers the consequences. These symptoms generally improve after appropriate medical management.

• Hypothyroidism: insufficient production of thyroid hormones can lead to dry and brittle hair, slow growth, and progressive fragility of the hair.
• Hyperthyroidism: an excess of thyroid hormones disrupts the follicular cycle and can promote dull hair as well as diffuse hair loss over the entire scalp.
• Cushing's Syndrome: this rarer cause of hair dryness and fragility is linked to a chronic excess of cortisol, which alters the quality of the hair fiber.
• Hormonal imbalances: menopause, pregnancy, and polycystic ovary syndrome (PCOS) alter sebum production. During menopause, the decrease in sebum particularly promotes dehydrated and dull hair.

Diagnosis is based on a blood test and a clinical examination. In practical application, treating the cause improves the hair fiber more effectively than a topical treatment used alone.

Deficiencies that weaken hair

A deficiency in vitamin D, biotin, or B vitamins represents one of the common causes of dry hair associated with nutritional deficiency. Iron deficiency reduces the oxygenation of follicles: the hair fiber thins, becomes coarse, and breaks more easily, especially in women with heavy periods. Zinc, in turn, is involved in keratin synthesis; an insufficiency can weaken the shaft and increase breakage on the lengths.

Other possible systemic diseases

Certain general diseases can also alter the quality of the hair fiber. Poorly controlled diabetes affects the microcirculation of the scalp: follicles receive less oxygen and nutrients, which progressively thins the shaft before hair loss appears.

Infectious diseases such as Covid-19, severe flu, or mononucleosis can trigger telogen effluvium. Diffuse hair loss then appears two to three months after the acute episode. Systemic lupus erythematosus can also cause significant hair loss, sometimes reversible with treatment depending on the extent of the lesions.

Persistent hair degradation, especially when accompanied by other symptoms, warrants professional advice.

Brittle hair caused by an underlying condition

Not all texture changes can be explained by external aggressions. The combination of dry and brittle hair with general symptoms may reveal a medical cause. These signs deserve to be identified quickly to preserve hair and overall health.

Warning signs not to ignore

A suddenly altered texture, with hair becoming very dry, coarse, and dull, without any change in routine or recent chemical aggression, constitutes a warning sign. More caution is needed when this transformation is accompanied by other symptoms suggesting a deterioration in health.

• Associated unusual fatigue: brittle hair associated with persistent fatigue, dry skin, or unexplained weight variation may indicate a thyroid disorder or severe deficiency.
• Rapid and unexplained degradation: intense dryness that appeared suddenly, without an identifiable cause in habits, warrants a medical consultation within weeks.
• Associated extra-capillary symptoms: symptoms of dry eyes, joint pain, or dry mouth may suggest Sjögren's syndrome, an autoimmune disease that affects exocrine glands and can also weaken the hair fiber.

The absence of improvement after several weeks of appropriate care also constitutes an important signal. A poor diet can amplify the manifestations, but if dietary corrections are not enough, an underlying medical cause should be considered, beyond just the hair routine.

Breakage or hair loss

Dry and damaged hair often breaks on the lengths. This breakage should be distinguished from hair loss at the root: the former concerns the weakened hair shaft, while the latter comes from the follicle and manifests as entire hairs, sometimes accompanied by their bulb. This distinction guides the diagnosis and the examinations to be planned.

Diffuse hair loss appearing two to three months after a severe infection corresponds to telogen effluvium: under the effect of physiological stress, the follicle prematurely enters the resting phase. This form of alopecia is generally reversible. Conversely, patchy hair loss associated with hair fragility can signal an autoimmune disease, such as alopecia areata or lupus.

When the scalp is affected

Seborrheic dermatitis is a chronic inflammatory dermatosis that evolves in flare-ups, linked to an abnormal proliferation of Malassezia yeasts. It affects the scalp in 95% of cases and causes dandruff, itching, and red plaques covered with greasy, white, or yellowish scales. Hair loss can be associated with it and accentuate existing fragility. Diseases responsible for dry hair cover a wide spectrum, from hormonal disorders to infection, including inflammatory dermatoses. Diseases responsible for dry hair require appropriate management.

Scalp psoriasis is another inflammatory dermatosis. It can lead to dryness, scaling, and localized hair fragility. In both situations, one month of self-medication without results warrants medical or dermatological advice. Without a precise diagnosis, prolonged self-treatment delays care and can worsen the condition of the scalp over time.

Care for dry hair and sensitive scalp

When a medical cause is identified or suspected, topical treatments do not replace prescribed treatment. However, they can limit breakage, improve the comfort of the lengths, and support the hair fiber during the assessment.

Medical assessment before care

Before initiating care for a sensitive scalp, a blood test is indicated if the dryness remains unexplained or worsens. A doctor or dermatologist may look for an iron, zinc, or vitamin D deficiency, as well as TSH abnormalities and hormonal markers. This diagnosis guides overall management.

• Thyroid assessment: TSH levels help detect hypothyroidism or hyperthyroidism. These disorders can cause hair symptoms, which improve with appropriate medical treatment.
• Deficiency assessment: serum iron, ferritin, zinc, vitamin D, and B vitamins help identify an active nutritional deficiency likely to weaken the hair fiber.
• Hormonal assessment: evaluation of androgens, estradiol, and other hormonal markers can be particularly useful in cases of PCOS, menopause, or progressive androgenetic alopecia.

After correcting a deficiency, hair recovery takes between 6 and 24 months depending on the age of the deficiency, the state of the follicle, and the quality of the diet. In addition, this monitoring helps to objectify progress on the density and resistance of the fiber. The difference is seen over time.

Gentle routine against breakage

Castor oil baths, aloe vera masks, and the application of pure shea butter are among the traditional treatments for very dry hair. To deepen the care of dry and brittle hair, Elyara details the steps of a restorative routine, from mask to final rinse.

• Gentle sulfate-free shampoo: with a pH between 4.5 and 5.5, glycerin and panthenol, it is used two to three times a week to preserve protective sebum without further drying the hair fiber.
• Phytokeratin mask: applied one to two times a week to clean, towel-dried hair for 10 to 15 minutes, it provides amino acids similar to natural keratin, which strengthen the shaft and reduce breakage.
• Conditioner after each wash: applied to the lengths and ends, it helps smooth the cuticles, reduce friction, and limit mechanical breakage.

Provitamin B5 retains water in the heart of the hair fiber, while aloe vera hydrates and soothes a reactive scalp. Argan, jojoba, or castor oils then help maintain this hair hydration on the lengths.

Gestures that preserve the hair fiber

Excessive heat damages keratin: beyond 120°C, the hair fiber cracks, becomes dull, and breaks in its most vulnerable areas. A heat protectant rich in polyphenols remains essential before any heat styling, with the device held at least 15 centimeters from the hair.

• Rinsing with lukewarm water: maintain a maximum temperature of 35 to 37°C to avoid opening the cuticles, then finish with a cold spray to smooth the cuticle and restore shine.
• Gentle drying: blot hair with a microfiber towel, without rubbing, and favor air drying. If a hairdryer is necessary, use it at a distance, on cool air, to limit dehydration.
• Brushing on dry hair: avoid aggressive brushing on wet hair, as it promotes micro-cuts and weakens the shaft. Too-tight hairstyles also accentuate mechanical damage to the lengths.

Chlorine, limescale, and UV rays deposit residues on the hair fiber, which can inhibit hydration and stiffen the hair. A satin pillowcase reduces nocturnal friction responsible for breakage. To complete this method, Elyara's hair routine for dry hair brings together the steps, from washing to leave-in care, to protect and repair the hair fiber over time.

Frequently asked questions