Medically reviewed by Vicky Davis, FNP
Written by Our Editorial Team
Last updated 2/19/2021
By the time you’re born, you’ve already developed all the hair follicles you’ll ever have.
Over the course of your life, these follicles go through a predictable cycle of hair growth that consists of three phases: anagen, catagen, and telogen.
Each of these three phases follows its own timeline which is affected by numerous factors including nutrition, age, genetics, and overall health.
Though you cannot modify certain details like the number of hair follicles you have or the thickness and texture of your hair, the rate at which your hair grows may change over time.
Aside from lifestyle choices, the cycle of hair growth can be altered by uncontrollable factors such as exposure to toxins or chemical medications.
Anagen effluvium is a form of hair loss triggered by a stressor such as a serious infection, exposure to toxins, or harsh medical treatments such as chemotherapy.
This type of hair loss may cause you to lose a significant number of hairs all at once, resulting in a temporary diffuse thinning of hair on the scalp. The good news is, it’s usually temporary.
Below, we’ve delved deep into the subject of anagen effluvium to explore what it is, what causes it, and whether it can be reversed. Finally, we’ve provided a list of science-backed treatment options that may help you regrow your hair.
Every hair on your body grows from a follicle underneath the skin. The hairs are fed by tiny blood vessels that deliver oxygenated blood and essential nutrients to fuel growth.
The first stage of the hair growth cycle is the anagen or growing phase. This phase can last for several years before the hairs move into the catagen phase for about ten days then finally transition into the telogen phase.
The final phase is one in which the follicles rest for two to four months before the old hair falls out to make room for new growth.
Effluvium is a term used to describe active hair loss of more than 100 hairs per day over a period of two to four weeks. This hair loss is typically classified according to the stage of the growth cycle in which the hairs are shed.
Anagen effluvium, then, refers to abrupt hair loss affecting hairs in the growing phase. This loss is generally triggered by an event or stressor that impairs the metabolic activity of the hair follicle. One of the most common causes for anagen effluvium is cancer treatment.
Also known as chemotherapy-induced alopecia, a nonscarring form of alopecia, anagen effluvium is often reversible.
Anagen effluvium is the result of severe trauma — typically toxicity or inflammation — that impairs the mitotic or metabolic activity of the hair follicles in the anagen phase.
Exposure to chemotherapeutic agents like antimetabolites, alkylating agents, and mitotic inhibitors is often to blame. Radiotherapy, infection, and autoimmune disease can also trigger this form of hair loss.
Unlike conditions like telogen effluvium which pushes the hairs into the telogen phase, resulting in premature shedding, anagen effluvium weakens the hair shaft, making it more susceptible to breakage. In some hairs, it may prevent hair formation.
Shedding of the damaged hairs usually takes place within 14 days of the offending stimulus. Fortunately, anagen effluvium is typically reversible — the hair growth cycle will resume once the treatment has been discontinued.
Generally speaking, treatment for anagen effluvium is aimed at limiting the amount of time the patient suffers from hair loss.
Because anagen effluvium is typically triggered by chemotherapy or radiation, treatment specifically for hair loss may not be necessary. In many cases, patients experience complete recovery within three to six months of completing their course of treatment.
The only treatments that have been supported by research to prevent or reduce the duration of anagen effluvium are scalp cooling therapy and topical minoxidil.
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Hair loss is a common side effect of chemotherapy and radiation treatments. According to a 2018 study, anagen effluvium was the most common adverse effect (78.6 percent) seen in a total of 1,000 patients undergoing chemotherapy.
Scalp cooling, also known as scalp hypothermia, has been found to help prevent hair loss in patients undergoing chemotherapy.
This treatment works by restricting the blood vessels in the scalp to reduce blood flow, limiting the amount of chemo medication that reaches the hair follicles. It can be accomplished using ice packs, cooling caps, or a scalp cooling system.
In one study involving 142 women with breast cancer, more than 50 percent of patients who received scalp cooling kept most or all of their hair.
Minoxidil is a topical medication approved by the FDA for treating hair loss. Available in liquid and foam forms, topical minoxidil comes in 2% and 5% concentrations.
Though the exact mechanism through which minoxidil improves hair growth is unknown, research shows it may trigger hair follicles to enter the growth phase early.
In a large 2004 study, over 84 percent of male participants found minoxidil “very effective,” “effective” or “moderately effective” in promoting hair growth over 12 months of treatment.
The thing to keep in mind is that it may take several months for the effects of minoxidil to be noticeable. Several studies have shown, however, that topical minoxidil may reduce the period of baldness by an average of 50 days.
Anagen effluvium is a common side effect of chemotherapy treatments but the good news is it is often temporary. Many patients experience regrowth within just a few weeks or months of stopping treatment. Some even experience regrowth during treatment.
If you’re looking for a way to boost hair growth in the meantime, however, hair loss treatments like minoxidil could help.
If you’re losing your hair and you’re not sure what is causing it, it’s best to speak to your healthcare provider.
Your healthcare provider can help determine the underlying cause of your hair loss and suggest a safe and effective form of treatment.