7 Causes of Telogen Effluvium

Telogen effluvium is a form of diffuse hair shedding that happens when more hairs than usual are pushed into the resting phase of the hair cycle. It is a reactive form of hair loss because it tends to happen in response to an internal trigger such as stress, hormonal change, nutritional deficiency, or inflammation. Telogen effluvium does not damage the follicle permanently, which means recovery is possible once the underlying cause is identified and addressed.

1. Hormonal Changes

Hormonal fluctuations are a common cause of increased shedding. Shifts in oestrogen, progesterone, and androgen levels can affect how long hair stays in the growth phase and how stable the overall cycle remains. Both underactive and overactive thyroid function can increase the number of hairs that prematurely enter the telogen (resting) phase. Other hormones, including prolactin, growth hormone, and IGF-1, also influence follicle behaviour, follicular activity, and tissue repair, which can alter cycling when dysregulated. Hormone changes can reflect wider changes in stress levels, sleep quality, metabolic health, and nutritional status.

2. Stress and High Cortisol

Poor sleep, overworking, skipping meals, illness, anxiety, nutritional deficiency, blood sugar instability, chronic inflammation and overtraining can all affect the hair growth cycle. High cortisol levels from chronic stress oppose growth signals, leading more hairs to exit the growth phase and enter the telogen (resting) phase. Chronically high levels of cortisol break down components of the dermis by breaking down collagen and elastin, leading to a thinner, shallower and less elastic dermis. Under these conditions, telogen hairs are more easily pulled out during brushing and washing. Cortisol also inhibits stem cell activity, which prevents new growth once the hair has shed. This leaves empty follicles and lowers overall hair density.

3. Macronutrient and Micronutrient Imbalance

Hair follicles are extremely metabolically expensive, which means they rely on a steady supply of energy, amino acids, vitamins, minerals, and essential fats to grow well. When meals are skipped or the diet is dominated by processed foods, the body may lack the raw materials needed to support healthy hair growth. Iron, vitamin D, zinc, vitamin B12, folate, and adequate protein all play important roles, but so does the overall quality and consistency of the diet. A broader pattern of poor food quality, unstable blood sugar, and reduced nutrient availability will affect the hair growth cycle.

4. Medical Conditions

Thyroid disease, iron deficiency anaemia, inflammatory bowel disease, polycystic ovary syndrome, endometriosis, autoimmune conditions, haemochromatosis, and other chronic health issues can all affect the hair growth cycle. Many of these conditions are linked to inflammation, altered iron handling, hormone disruption, poor nutrient absorption, or wider metabolic stress, so the relationship is not always straightforward. Certain conditions can trigger shedding, or shedding can be an early warning sign of a developing condition.

5. Medication and Drug Exposure

Retinoids, anticoagulants, antidepressants, beta blockers, and some cholesterol-lowering drugs can trigger telogen effluvium by disrupting the normal timing of the hair cycle. The exact mechanism varies between drugs and is not always fully understood, but the overall effect is the same: the hair growth cycle becomes less stable, and more hairs are shed than usual.

6. Postpartum Shedding

After pregnancy, many women notice a sudden increase in shedding. During pregnancy, higher oestrogen levels keep more hairs in the growth phase for longer. Once those hormone levels fall after childbirth, a larger percentage of hairs enter the resting phase together and shed over the following months. This type of hair loss is usually temporary, unless there are underlying nutritional or hormonal imbalances that prevent the mass re-entry into the growth phase.

7. Inflammation of the scalp

The scalp microbiome can also influence shedding when the local environment becomes inflamed or imbalanced. In a healthy follicle, the resting telogen hair is actively anchored within the follicle by specialised adhesion structures, including desmosome-related proteins such as desmoglein 3. If the scalp becomes chronically inflamed, or if microbial overgrowth and biofilm formation increase local proteolytic activity, this may weaken the adhesion machinery that helps retain the hair fibre. This promotes earlier release of hairs that would otherwise remain anchored for longer. This mechanism is still being studied, but it explains why some people experience ongoing shedding in the presence of scalp irritation, flaking, inflammation, or microbial imbalance.  

Conclusion

Interventions such as PRP, mesotherapy and minoxidil can provide some support, but they do not address the root cause of telogen effluvium on their own. The key to improving telogen effluvium is identifying the triggers that are disrupting the hair growth cycle rather than focusing only on the shedding. The most effective approach is to look beneath the surface and understand why the scalp has been pushed out of balance in the first place.