Can the influenza (flu) vaccine cause rash and alopecia (hair loss)?

Can the Flu Vaccine Cause Rash and Hair Loss?

Yes, the influenza vaccine can rarely cause rash as an allergic or hypersensitivity reaction, and hair loss has been reported in extremely rare cases, though causality remains uncertain.

Rash Following Influenza Vaccination

Documented Allergic Reactions

• Immediate allergic reactions including hives (urticaria) rarely occur after influenza vaccination, typically resulting from hypersensitivity to vaccine components, most commonly residual egg protein 1.
• Rash was among the most frequently reported adverse events in the Vaccine Adverse Event Reporting System (VAERS), though determining causality is difficult with passive surveillance systems 1.

Types of Cutaneous Reactions

• A systematic review of cutaneous reactions in adults found that erythematous macules/papules/plaques were the most common skin manifestations (56.7% of cases), followed by vasculitic and purpuric rashes (16.7%) and morbilliform rashes (10%) 2.
• Nearly all patients (96.7%) with documented cutaneous reactions experienced complete resolution with treatment 2.
• One case report documented serum sickness-like reaction with fever, rash, and polyarthralgia occurring 5 days post-vaccination, which resolved over 5 weeks with treatment 3.

Clinical Context

• Hypersensitivity to thimerosal (when present in vaccines) typically manifests as local, delayed-type reactions rather than widespread rash 1.
• Persons with documented IgE-mediated hypersensitivity to eggs or history of anaphylaxis should not receive influenza vaccine 1, 4.

Hair Loss Following Influenza Vaccination

Evidence for Association

• Hair loss after vaccination is extremely rare and causality remains uncertain, with only 60 evaluable reports submitted to VAERS since 1984 coded for alopecia after any immunization 5.
• Of these 60 cases, 46 had received hepatitis B vaccines (not influenza vaccines), with only 16 showing positive rechallenge (hair loss after vaccination on more than one occasion) 5.
• The study concluded there "may be an association, probably very rare, between vaccinations and hair loss" but noted that biased case ascertainment could explain apparent patterns 5.

Mechanism Considerations

• Hair loss is NOT mentioned in any ACIP guidelines as a recognized adverse effect of influenza vaccination 1, 6, 7.
• One report described recurrence of alopecia areata after COVID-19 vaccination in patients with prior history, speculating that vaccine-induced immune activation may trigger autoimmune mechanisms in predisposed individuals 8.
• Multiple pathophysiologic mechanisms may be responsible if an association exists, and clinical features varied widely in reported cases 5.

Clinical Recommendations

For Rash

• Evaluate patients with rash post-vaccination for immediate hypersensitivity reactions (hives, angioedema, respiratory distress, anaphylaxis) that require urgent intervention 1, 4.
• Most cutaneous reactions are self-limited and resolve with symptomatic treatment including antihistamines, NSAIDs, or short-course corticosteroids 2, 3.
• Consider alternative causes, as respiratory illness and other symptoms after vaccination often represent coincidental illness unrelated to the vaccine 1, 6, 7.

For Hair Loss

• If hair loss occurs after influenza vaccination, thoroughly investigate other causes including medications, nutritional deficiencies, thyroid disorders, and autoimmune conditions, as this is not an established vaccine adverse effect 7.
• Document and report any clinically significant adverse events to VAERS, even without certainty of causation 4.
• The temporal association alone does not establish causality given the rarity of reports and lack of biological plausibility 5.

Important Caveat

• The influenza vaccine contains only noninfectious killed viruses and cannot cause influenza 1, 6, 7.
• The benefits of influenza vaccination in preventing influenza and its severe complications far outweigh the potential risks of rare adverse effects 7.