Hair loss due to illness, stress or medication
Why is my hair suddenly falling out?
Sudden hair loss can be alarming. You may immediately think of permanent baldness or hereditary hair loss (androgenetic alopecia). In many cases, this is not the case. After illness, high fever, surgery, stress, or medication use, hair loss is often temporary and reactive: the body experiences a shock, the hair cycle is temporarily disrupted, but the hair roots remain alive.
Reactive hair loss is an umbrella term doctors use for temporary forms of hair loss that occur in response to a physical change. The hair roots themselves usually remain healthy, but the normal hair growth cycle is temporarily disturbed.
The most common form is called telogen effluvium: after illness, fever, or the use of certain medications, many hairs enter the resting phase at the same time and fall out several months later.
Dermatologist Dr. Petra Dikrama explains in Huisarts & Wetenschap (2024):¹
“In telogen effluvium, the hair roots are not destroyed but temporarily at rest. Once the underlying cause disappears, hair growth resumes spontaneously.”
In some situations, such as during chemotherapy, another form occurs: anagen effluvium. In this case, hair growth stops abruptly because medications temporarily damage actively dividing hair cells. Even then, hair usually grows back once the treatment has ended.
How hair growth works
Hair grows according to a fixed cycle with three phases:
- Growth phase (anagen phase) – hair grows approximately one centimeter per month.
- Transition phase (catagen phase) – hair growth temporarily stops.
- Resting phase (telogen phase) – hair falls out and makes room for a new hair.
Normally, 80–90% of your hair is in the growth phase. During illness, stress, or medication use, this balance shifts and too many hairs enter the resting phase at the same time, falling out months later. Hair follicles are particularly sensitive to changes in the body. Stress, fever, or hormonal fluctuations can temporarily disrupt the growth cycle. A hair follicle can perceive stress just like the rest of the body. This response can cause temporary hair shedding.²
Types of hair loss related to illness or medication³
Hair loss can have many different causes — ranging from illness and medication to stress or immune system disorders. This makes it difficult to determine what is happening and how long recovery may take. Dermatologists distinguish several types of hair loss. Some are temporary, while others require medical treatment or monitoring. In most cases, the hair roots remain intact and hair regrows once the body recovers or the triggering factor is removed.
| Type of hair loss | What happens in the scalp? | When does hair loss start? | Typical recovery time |
|---|---|---|---|
| Telogen effluvium (TE) | Many hairs shift simultaneously from the growth phase to the resting phase (telogen). Temporary diffuse thinning over the entire scalp. | 1–3 months after illness, fever, surgery, stress, or medication. | 3–12 months after recovery; gradual regrowth. |
| Anagen effluvium (chemotherapy-related) | Chemotherapy or radiation stops cell division in active hair roots. Rapid, often complete hair loss. | Days to weeks after starting treatment. | 6–12 months after completing therapy; first regrowth after 4–8 weeks. |
| Autoimmune hair loss (e.g. alopecia areata or Graves’ disease) | The immune system attacks the hair roots. Patchy or diffuse hair loss. | Sudden onset, sometimes after infection or stress. | Variable: weeks to months; may recover spontaneously or recur. |
| Medication-induced hair loss | Certain medications temporarily disrupt the hair growth cycle, causing diffuse shedding. | Weeks to months after starting medication. | Usually full recovery within 3–6 months after stopping or adjusting medication. |
| Stress-related hair loss | Stress hormones (such as cortisol) temporarily disrupt the growth cycle. More hairs enter the resting phase → diffuse thinning. | Weeks or months after a stressful period. | 3–6 months once balance and recovery return; relaxation supports regrowth. |
| Chronic telogen effluvium | Long-term disruption or incomplete recovery of the hair cycle; hair remains thinner and loses volume. | 1–3 months after repeated stress, hormonal or metabolic imbalance. | May last for years; sometimes persistent. Causes should be investigated (iron, thyroid, hormones). |
Hair loss after illness or fever
After an infection, surgery, or high fever, the body may temporarily stop hair growth. Energy is redirected to vital organs rather than the hair roots. Hair loss usually becomes noticeable 2 to 5 months after the triggering event. In acute telogen effluvium, hair density typically recovers within three to twelve months.³
Hormonal changes can also temporarily disrupt hair growth, for example:
- after childbirth, when hormone levels drop rapidly;
- with thyroid disorders, such as an underactive or overactive thyroid;
- during menopause.
In all of these situations, hair loss usually begins 2 to 4 months after the hormonal change and resolves spontaneously once balance in the body is restored. It is rarely permanent: the hair roots remain active but need time to restart their growth cycle.
Hair loss caused by medication
Some medications can temporarily cause hair loss. In most cases, this is a temporary reaction of the hair roots: they switch too early to the resting phase (telogen effluvium). Hair loss is evenly distributed across the scalp, not permanent, and hair regrows within a few months once the body adapts to the medication or its use is discontinued.⁷⁻⁸
Which medications can cause this?
The following medication groups are most commonly involved:⁴⁻⁷⁻⁸⁻⁹⁻¹⁰
| Medication group | What happens? | When does it start? | Recovery after stopping |
|---|---|---|---|
| Blood thinners (Xarelto, heparin, enoxaparin, warfarin) | Accelerate the shift of hairs to the resting phase (telogen effluvium). | 2–4 months after starting. | 3–6 months. |
| Beta blockers (for high blood pressure or palpitations) | Reduced scalp blood flow → more hairs in resting phase. | Weeks to months. | 3–6 months. |
| Antidepressants and mood stabilizers(SSRIs, tricyclics, lithium, valproic acid) | May cause hair loss or changes in hair structure. | Weeks to months after starting. | Usually 3–6 months after stopping. |
| Thyroid medication (levothyroxine, thiamazole) | Hormonal imbalance → temporary hair loss. | Weeks to months. | 3–6 months. |
| Oral contraceptives | Hormonal changes → temporary or pattern-like hair loss. | Several months after starting or stopping. | 3–6 months. |
| Vitamin A–derived medications(retinoids such as isotretinoin) | Slower hair growth or thinner hair. | After weeks to months. | Recovery within several months. |
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Sudden hair loss - telogen effluvium
references:
1. Dikrama P. Diffuse hair loss due to telogen effluvium. Family Practice & Science. 2024; 67(2): 112–115.
2. Pope R, et al. The Biology of Hair Follicles. The New England Journal of Medicine. 1999;341(7):491-7.
3. Dutch Society for Dermatology and Venereology (NVDV). Telogen Effluvium. Utrecht; 2023. NVDV Telogen Effluvium Guidelines
4. Daunton A. Et al. Chronic Telogen Effluvium: Is It a Distinct Condition? A Systematic Review. American Journal of Clinical Dermatology. 2023;24(4):513-520.
5. Sinclair R. Chronic Telogen Effluvium: A Study of 5 Patients Over 7 Years. Journal of the American Academy of Dermatology. 2005;52(2 Suppl 1):12-6.
6. Whiting DA Chronic Telogen Effluvium. . Dermatologic Clinics. 1996;14(4):723-31.
7. Chien Yin GO et al. Telogen Effluvium - A Review of the Science and Current Obstacles. Journal of Dermatological Science. 2021;101(3):156-163.
8. Phillips TG et al. Hair Loss: Common Causes and Treatment. American Family Physician. 2017;96(6):371-378.
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10. Shapiro J. Hair loss in women. N Engl J Med. 2007; 357(16): 1620-1630.
11. Kanker.nl (from the Dutch Cancer Society, the Dutch Cancer Society, and the Netherlands Cancer Institute); Hair loss and scalp cooling during chemotherapy. April 2025. Available at: https://www.kanker.nl/soorten-behandelingen/chemotherapie/de-behandeling-met-chemotherapie/haaruitval-en-hoofdhuidkoeling-tijdens-chemotherapie .
12. Dutch Society for Dermatology and Venereology (NVDV). Alopecia areata Guideline (2024): Alopecia areata Guideline 2024 - NVDV
13. Huidvelden.nl - Alopecia areata https://www.huidverzekeringen.nl/zakboek/dermatosen/atxt/AlopeciaAreata.htm
14. Udompanich S, et al. Hair and Scalp Changes in Cutaneous and Systemic Lupus Erythematosus. American Journal of Clinical Dermatology. 2018;19(5):679-694.
15. Chaker L, et al. Hyperthyroidism. Lancet (London, England). 2024;403(10428):768-780.
16. O'Sullivan JDB et al. The impact of perceived stress on the hair follicle: a psychoneuroendocrine and neuroimmunological puzzle. Front Neuroendocrinol. 2022;66:101008.
17. Arck PC et al. Stress inhibits hair growth in mice via neuropeptide substance P–dependent pathways. Am J Pathol. 2003;162(3):803-14.
18. Ahn D et al. Psychological stress-induced pathogenesis of alopecia areata: autoimmune and apoptotic pathways. Int J Mol Sci. 2023;24(14):11711.
19. Xiao X et al. M1 polarization of macrophages promotes stress-induced hair loss via interleukin-18 and interleukin-1β. J Cell Physiol. 2024;239(4):e31181.
20. Dikrama P, Buis P. Diffuse hair loss due to telogen effluvium. Family Practice & Science. 2024;67(2):112-115.
21. Randall VA et al. Mechanisms of Action of Minoxidil in Hair Regrowth. J Am Acad Dermatol. 2020; 82(6): 1346–1354.
22. Huang C, et al. JAMA Dermatol. 2021;157(8):963–970.
23. Marks DH, et al. The medical and psychosocial associations of alopecia: recognizing hair loss as more than a cosmetic concern. Am J Clin Dermatol. 2019;20(2):195-200.
24. Schielein MC, et al. Stigmatization caused by hair loss – a systematic literature review. J Dtsch Dermatol Ges. 2020;18(12):1357-1368.
25. Barkauskaite R, et al. Therapeutic implications of psychological state in patients with alopecia areata: a qualitative study. Dermatol Ther. 2020;33(6):e14269.
