Does Ajovy cause hair thinning? A closer look at clinical trials vs. anecdotal reports

October 7, 2025 •

4 min read

While large-scale clinical trials for the migraine medication Ajovy did not document hair loss as a common side effect, anecdotal and post-marketing reports suggest a possible link between treatment and hair thinning. Patients and healthcare providers must understand the distinction between observed side effects in controlled studies and voluntary real-world reports.

Quick Summary

An examination of available evidence reveals that Ajovy's clinical trials did not report hair loss, yet post-marketing data and anecdotal reports indicate a potential association with hair thinning. Factors like underlying migraine stress and differences from other migraine treatments must also be considered.

Key Points

Clinical Trials vs. Reality: Ajovy's initial clinical trials did not report hair loss, but post-marketing reports and patient anecdotes suggest a possible, though likely rare, association with hair thinning.
Causation Not Proven: Voluntary reports of adverse events through systems like the FDA's FAERS do not prove that Ajovy directly caused the hair loss. The correlation could be coincidental.
Migraine Stress: The stress associated with chronic migraine itself can be a cause of hair loss, making it difficult to isolate the medication as the culprit.
CGRP Class Effect: Evidence suggests that hair loss may be a potential class effect of CGRP inhibitors, though larger studies are needed to confirm the association.
Seek Medical Advice: Patients experiencing hair thinning while on Ajovy should consult their healthcare provider to investigate all potential causes and discuss the best course of action.
Reversibility: In some anecdotal cases, hair loss has been reported to reverse after discontinuing the medication.
Not an Established Side Effect: Hair loss is not listed as a known or common side effect in Ajovy's official clinical trial data or prescribing information.

What is Ajovy (fremanezumab)?

Ajovy (fremanezumab) is a prescription medication used for the preventive treatment of migraine in adults. It belongs to a newer class of drugs called calcitonin gene-related peptide (CGRP) inhibitors. CGRP is a protein involved in pain signaling during a migraine attack, and by blocking it, Ajovy helps reduce the frequency and severity of migraines. Administered as a subcutaneous injection, patients can receive a dose monthly or quarterly. This targeted approach to migraine prevention is one of the key differences between CGRP inhibitors and older preventative medications, which often target other pathways in the body and come with a wider range of side effects.

Clinical Trials: No Hair Loss Reported

When Ajovy was submitted for FDA approval, comprehensive clinical trials were conducted to assess its safety and efficacy. In these controlled studies, hair loss was not reported as a side effect. The most commonly reported side effect during trials was injection site reactions, such as pain, redness, or swelling, which were typically mild to moderate. These clinical trial findings provided the initial safety profile for Ajovy and other CGRP inhibitors, establishing that they did not appear to cause widespread hair loss in the study populations.

Post-Marketing and Anecdotal Evidence

Despite the results from clinical trials, the real-world experience for some patients has been different. Since Ajovy and other CGRP inhibitors became available, post-marketing surveillance through systems like the FDA Adverse Event Reporting System (FAERS) has shown reports of alopecia (hair loss).

In fact, a 2022 study analyzed FAERS data and found significant 'alopecia signals' associated with CGRP inhibitors, including fremanezumab (Ajovy). It's crucial to understand that FAERS reports are voluntary and do not prove causation. Many factors, including how long a drug has been on the market, can influence reporting rates. Anecdotal reports can also be found in online patient forums and communities, with some individuals attributing their hair thinning to Ajovy use. A specific case report also detailed localized injection site alopecia in a patient using fremanezumab.

Potential Mechanisms and Explanations for Hair Loss

It is not yet fully understood why some individuals may experience hair thinning while on Ajovy, especially when clinical trials did not show this effect. Several theories and contributing factors exist:

Vascular disruption: CGRP plays a role in vasodilation (blood vessel widening). Inhibiting CGRP could potentially affect the blood supply to hair follicles in some individuals, leading to a disruption of the hair growth cycle.
Inflammatory response: As a newer class of medication, the long-term effects on the body's inflammatory system are still being studied. An inflammatory response near the injection site could trigger hair loss in a localized area, as suggested by a case report.
Chronic migraine stress: Migraine itself is a chronic, painful condition that can cause significant physical and emotional stress. Stress is a well-known cause of temporary hair shedding, or telogen effluvium. For many patients, it can be difficult to disentangle whether the medication or the underlying condition is responsible for their hair loss.
Comorbid conditions: Many health conditions that can cause hair loss are also comorbid with migraine disease, including certain autoimmune disorders.

Comparing Ajovy to Other Migraine Medications

Comparing Ajovy to other treatments helps put the hair loss issue into perspective. While hair loss is a potential side effect with CGRP inhibitors based on post-marketing data, it is a well-known side effect of several older migraine medications.


Feature	Ajovy (fremanezumab)	Topamax (topiramate)	Aimovig (erenumab)	Nurtec ODT (rimegepant)
Drug Class	CGRP Monoclonal Antibody	Anticonvulsant	CGRP Monoclonal Antibody	CGRP Receptor Antagonist (gepant)
Hair Loss in Clinical Trials	Not reported	Known side effect	Not reported	Not reported
Hair Loss in Post-Marketing Reports	Anecdotally reported; disproportionate reporting noted in FAERS	Well-documented side effect	Post-marketing reports exist; disproportionate reporting noted	Less frequent reports than monoclonal antibodies
Key Mechanism	Blocks CGRP ligand	Several mechanisms affecting neurotransmitters	Blocks CGRP receptor	Blocks CGRP receptor

What to do if you notice hair thinning

If you are using Ajovy and notice changes in your hair, it is important to communicate with your doctor. They can help determine the potential cause of the hair loss and distinguish it from other factors. Here are some key steps you can take:

Talk to your doctor: Inform your healthcare provider about any hair thinning or loss. They can review your entire medication regimen, check for other possible medical conditions, and help you decide on the best course of action.
Evaluate other medications: Hair loss can be a side effect of other drugs you may be taking, including older migraine preventatives.
Rule out other causes: Your doctor can check for other potential causes, such as stress, nutritional deficiencies, hormonal changes, or other medical issues.
Consider dose adjustment or change: In some cases, your doctor may suggest adjusting the dosage or switching to a different migraine preventative to see if the hair loss subsides. An anecdotal report noted hair loss reversed after stopping Ajovy.
Report the side effect: If you suspect Ajovy is the cause, report the adverse event to the FDA's MedWatch program.

Conclusion

While Ajovy’s clinical trials did not show hair loss as a common side effect, post-marketing surveillance and anecdotal evidence indicate that a small number of patients may experience hair thinning. Given the voluntary nature of these reports, it is not definitively proven that Ajovy is the direct cause, and other contributing factors, such as stress from migraine or other medical issues, should be considered. Anyone experiencing hair thinning while on Ajovy should speak with their doctor to explore the cause and potential management strategies. The key takeaway is to rely on a thorough medical evaluation rather than assuming the medication is the sole reason for hair loss.

For more information on the FDA's drug reporting system, you can visit the FDA MedWatch website.

Frequently Asked Questions

No, hair loss was not reported as a side effect in the large-scale clinical studies conducted for Ajovy (fremanezumab) prior to its FDA approval.

Evidence suggesting a link comes primarily from post-marketing surveillance, including voluntary reports to the FDA Adverse Event Reporting System (FAERS) and anecdotal patient reports.

No, hair loss is considered a rare or uncommon side effect of Ajovy, as it was not observed in clinical trials. It has only been reported anecdotally since the drug became available on the market.

Yes, chronic stress is a known cause of hair shedding (telogen effluvium). Since migraines are a stressful condition, it can be difficult to determine if the medication or the underlying migraine disease is the cause of hair thinning.

The exact mechanism is not fully known. One theory is that inhibiting CGRP could disrupt the blood flow to hair follicles, potentially affecting the hair growth cycle. Another possibility is a localized inflammatory response, particularly at the injection site.

You should not stop taking Ajovy without first consulting your doctor. They can evaluate your symptoms, consider other potential causes, and discuss the risks and benefits of continuing or changing your treatment plan.

Unlike older migraine preventatives such as topiramate (Topamax), which are known to cause hair loss, hair thinning with Ajovy appears to be a much rarer, post-marketing reported side effect.