Brittle hair and illness: causes, alopecia, and treatments

Summary

• Which illness causes brittle hair?
• Alopecia and autoimmune diseases that weaken hair
• Brittle hair due to deficiencies and hormonal imbalances
• Best brittle hair care after an illness
• Natural treatments and remedies for brittle hair
• Frequently Asked Questions

Brittle hair can signal an internal imbalance: thyroid disorders, diabetes, hormonal imbalance, iron deficiency, or consequences of infectious diseases. Understanding the possible medical cause helps direct the diagnosis to a doctor as soon as breakage goes beyond simple mechanical origin. To learn more about brittle hair causes, this complementary reading provides useful insight.

Which illness causes brittle hair?

Brittle hair doesn't always come from over-brushing or a poorly chosen product. Sometimes, the hair fiber reflects an internal imbalance. Certain systemic diseases, metabolic or hormonal disorders, as well as several infections, can weaken the hair shaft and be accompanied by hair loss.

Systemic diseases and thyroid disorders

When dry hair becomes increasingly brittle, the thyroid should be investigated. In cases of hypothyroidism, metabolism slows down: the follicle functions sluggishly, which promotes dry and brittle hair, slower growth, and sometimes diffuse loss. Conversely, hyperthyroidism also disrupts the hair cycle, but due to overstimulation, with often more rapid loss.

• Hypothyroidism: slowed metabolism, with dry and brittle hair, slowed growth, and progressive fragility, generally improved after appropriate treatment.
• Hyperthyroidism: accelerated metabolism that disrupts the follicular cycle and can lead to diffuse hair loss across the entire scalp.
• Poorly controlled diabetes: impaired microcirculation, leading to less oxygen and nutrients for the follicles, especially during an episode of glycemic imbalance.

Diabetes does not act like a classic hormonal disorder. It is microcirculation that is at fault, with the hair gradually thinning before hair loss sets in. In the same medical register, certain infectious diseases such as Covid-19, severe flu, or mononucleosis can trigger telogen effluvium.

Infectious diseases and telogen effluvium

After a significant infection, loss of density does not always appear immediately. In fact, it is often the opposite: the hair loss occurs 2 to 3 months later, when the acute episode already seems to be behind you. This delay corresponds to the time required for follicles that have prematurely entered the telogen phase to release the affected hairs.

This picture can suggest a sudden worsening, whereas it is a delayed response to the initial illness.

When to consult for brittle hair

If brittle hair becomes a persistent problem, suggests an internal context, or is accompanied by general disorders, a medical consultation is indicated. A doctor can request a targeted assessment: iron, thyroid, hormonal status, sometimes other investigations depending on the symptoms. This diagnosis avoids merely treating the surface of the problem.

Regrowth is often possible when the cause is identified and corrected. This applies to a deficiency, an endocrine disorder related to hormones, or temporary effluvium. During this phase, Elyara's anti-breakage mask helps support weakened hair fiber, especially for lengths, particularly in cases of persistent dry or brittle hair.

Alopecia and autoimmune diseases that weaken hair

Certain forms of hair loss are neither due to simple temporary stress nor an isolated deficiency. They reflect an immune system reaction against the hair follicle. This immune-related alopecia covers several presentations, from a few patches to a much more widespread loss of hair and body hair.

The different forms of alopecia areata

Alopecia areata, or patchy hair loss, is an autoimmune disease in which hair follicles are attacked by the immune system. It most often causes sudden hair loss in well-defined, rounded patches. Conversely, androgenetic alopecia follows a different logic, linked to hormonal and genetic factors.

• Localized alopecia areata: one or more patches on the scalp, with sometimes favorable evolution under treatment.
• Alopecia totalis: complete loss of scalp hair, a more severe form requiring close dermatological monitoring.
• Alopecia universalis: diffuse involvement with loss of all body hair, including eyelashes and eyebrows.
• Ophiasis alopecia: band-like hair loss on the nape and temples, often more difficult to stabilize.

There is no definitive curative treatment for alopecia areata. However, local or injected corticosteroids, as well as Minoxidil, can support regrowth in certain forms. Scarring alopecia is due to a different mechanism: the follicle is destroyed by inflammation, infection, or burns, and regrowth is then no longer possible.

Autoimmune diseases and associated hair loss

Brittle hair that falls out can also accompany other immune conditions. Systemic lupus erythematosus can lead to significant hair loss, sometimes reversible with treatment, except in cases of scalp lesions leaving a scarring condition. In addition, certain thyroid diseases, such as Hashimoto's or Graves' disease, are among the common causes of diffuse hair loss.

Other autoimmune diseases, such as Sjögren's syndrome, dermatomyositis, scleroderma, or celiac disease, may include hair involvement among their secondary disorders. Their occurrence often relies on a genetic predisposition and environmental factors, especially certain viral infections.

Brittle hair due to deficiencies and hormonal imbalances

Nutritional deficiencies and hormonal variations are among the most common causes of brittle hair. Often, they accumulate. This is where the problem becomes complicated, because a hair fiber already weakened by insufficient intake reacts even worse to an internal imbalance. To distinguish a deficiency, hormonal disorders, or alopecia, a blood test remains the basis.

Iron, zinc, and essential vitamin deficiencies

A situation of brittle hair linked to a deficiency often indicates a deeper deficit than simple dryness. The hair fiber is mainly composed of proteins, especially keratin. As soon as the intake of amino acids, iron, zinc, or vitamin becomes insufficient, fragile hair loses resistance and growth slows down.

• Iron deficiency: it reduces oxygenation of the follicles and slows growth. This deficiency is common in women, especially in cases of heavy periods or a diet poor in iron.
• Zinc deficiency: it disrupts keratin synthesis and weakens the hair shaft, with more visible breakage on the lengths.
• Vitamin D and biotin deficiency: they weaken follicular activity and lengthen resting phases, which promotes slower growth.
• Dehydration and lack of lipids: they accentuate the dryness of the fiber, especially on textured, curly, or sensitized hair.

In practical application, a varied diet with enough proteins, iron, zinc, and B vitamins supports fiber reconstruction over time.

Iodine monitoring also has its place, as the thyroid directly influences the hair cycle. In cases of restrictive diets, persistent fatigue, or other associated disorders, this point should be checked promptly.

Hormonal imbalances and hair fragility

Persistent fragility can sometimes come from hormones as much as from diet. Pregnancy, postpartum, menopause, or certain thyroid dysfunctions alter the hair cycle. The hair grows less well, becomes thinner, and then breaks more easily.

Androgenetic alopecia is a common case. It combines genetic factors with increased sensitivity to androgens, with density gradually decreasing. In some women, this picture can be added to diffuse alopecia linked to a hormonal drop or the deficiencies described above. The difference lies in the duration: the longer the imbalance persists, the slower the recovery.

How long to recover after a deficiency

After correcting a deficiency, hair recovery takes time. It often takes between 6 and 24 months, depending on the age of the deficit, the state of the follicle, and the quality of the diet.

Regular medical follow-up allows for adjusting nutrient intake based on assessments. Food supplements can be useful, especially when a zinc, iron, or vitamin deficiency has been confirmed, but they support a global strategy. To also act on the hair fiber, external care has its place: phytokeratin for brittle hair, to be favored on the lengths, usefully complements the treatment.

Best brittle hair care after an illness

Once the medical diagnosis has been established and the internal cause addressed, the hair fiber requires specific external support. Topical treatments do not replace underlying treatment, but they help rebuild hair faster. Hair health is thus restored on two levels: internal balance, sometimes linked to a deficiency or a drop in vitamin, and the care applied to the hair fiber.

Phytokeratin, a benchmark reparative treatment

When it comes to treating brittle hair, phytokeratin remains a solid reference. This active ingredient, obtained from wheat, corn, or soy through enzymatic hydrolysis, has amino acids similar to those of natural keratin. Its low molecular weight promotes penetration into the cortex, without weighing down the lengths.

• Breakage reduction: up to 98% from the first brushing, thanks to the filling of cracks and sealing of damaged scales.
• Increased shine: +25% from the first application, then up to 45% with regular use.
• Improved elasticity: approximately 30% in one month, with less breakage during brushing and handling.
• Extended hydration: an invisible veil helps maintain hydration for 48 hours and limits dryness.

The Elyara nourishing mask incorporates this phytokeratin in a formula with 94% natural ingredients, with a pH of 4.2 that respects scalp balance. The Elyara formula is formaldehyde-free, vegan, and dermatologically tested: from the first applications, the hair fiber improves in feel and resists brushing better.

Vegetable oils and complementary natural active ingredients

In addition, certain active ingredients enhance the effectiveness of a treatment for damaged, brittle hair. Castor oil deeply nourishes and provides light protection against external aggressions. Shea butter helps restore the protective lipid film while soothing a sensitized scalp.

• Provitamin B5: it extends the internal hydration of the hair fiber for 48 hours after application.
• Aloe vera: it immediately hydrates and facilitates detangling of fragile hair after an illness.
• Argan oil: rich in omegas 3, 6, 9 and vitamin E, it nourishes the surface and improves the radiance of dry and brittle hair.

For occasional care, olive oil, virgin coconut oil, and wheat germ oil are also beneficial, to be preferred on the lengths.

Hair care routine adapted to very damaged hair

After an illness, a deficiency, or an episode that has weakened the hair fiber, the routine should remain simple and regular. For brittle hair, the phytokeratin mask should be applied 1 to 2 times a week to clean, towel-dried hair. For dry, colored, or very sensitized hair, a resting time of 10 to 15 minutes significantly improves the action of the active ingredients.

For a more intensive repair phase, an overnight application under a satin cap can be beneficial. This increases contact time with the hair fiber without weighing down fine hair. Once the mask is rinsed, the hair regains flexibility and is easier to detangle.

Fragile hair after treated hypothyroidism or after correcting a deficiency responds better to a consistent regimen: repairing shampoo, conditioner, then a weekly mask.

Natural Treatments and Remedies for Brittle Hair

Once the medical cause is identified and addressed, natural solutions can support hair reconstruction. Diet, targeted care, and daily habits work together to help brittle hair gradually regain strength.

Diet and Food Supplements to Strengthen Hair

Treating brittle hair often starts with your plate. A diet rich in protein, iron, and B vitamins provides the follicle with the necessary elements to produce a stronger fiber. Lentils, fatty fish, eggs, and green vegetables are therefore essential. In addition, seafood, vegetable oils, and nuts contribute essential fatty acids and zinc.

• Lentils and legumes: They provide non-heme iron and plant proteins; combining them with vitamin C improves iron absorption.
• Fatty fish and eggs: They provide omega-3s, biotin, and vitamin D, which are useful for hair fiber strength.
• Food supplements: Keratin, brewer's yeast, and B vitamins can be considered for a course of at least one month, especially in cases of identified deficiency or increased needs.

Practically speaking, a five-minute scalp massage can also stimulate microcirculation and facilitate the delivery of nutrients to the follicles.

Daily Habits and Routines Against Breakage

Reducing mechanical and thermal damage remains one of the first measures to implement. Brushing wet hair, overly tight hairstyles, and using irons above 150 °C put significant stress on the hair shaft. Spacing out shampoos also helps preserve the protective sebaceous film.

Repeated friction, chlorinated or salty water, and frequent chemical colorations weaken the cuticle. A soft brush, flexible hair ties, and a heat-protective spray are enough to significantly limit breakage on the lengths. Chronic stress can also disrupt the hair cycle, so regular practices like yoga, meditation, or sport support a more stable environment for regrowth.

Aggressive sulfates, certain denatured alcohols, and overly occlusive silicones can unbalance the hair fiber over washes. A gentle, sulfate-free shampoo remains a consistent base for maintaining brittle hair without adding unnecessary fragility.

Using a Phytokeratin Mask According to Your Hair Type

Phytokeratin is not used in the same way on all hair types. For fine hair, a three-minute application on the ends, twice a month, is often sufficient. For very fragile or colored hair, one to two applications per week for ten to fifteen minutes can support fiber reconstruction from the first uses.

After a period of stress or an iron, zinc, protein, or vitamin deficiency, the situation can improve in a few months with appropriate management. Conversely, a genetic or hormonal condition often requires prolonged medical follow-up: the difference lies in the duration.