Clinical bottom line
Allergic reactions to COVID-19 antiviral therapies are an emerging clinical concern as these treatments become more widely used. Current evidence suggests that while severe hypersensitivity reactions are rare, clinicians should maintain vigilance for immediate and delayed allergic responses. Diagnosis relies on a combination of clinical history, timing of symptom onset, and, when available, skin testing or graded drug challenges. Management strategies include prompt recognition, discontinuation of the suspected agent, and supportive care with antihistamines, corticosteroids, or epinephrine for anaphylaxis. Given the novelty of many COVID-19 antivirals, standardized protocols for allergy evaluation and desensitization remain under development. Clinicians should balance the benefits of antiviral therapy with the risks of allergic reactions, especially in patients with prior drug allergies or atopic predisposition.
What the evidence shows
COVID-19 antiviral therapies, including agents such as remdesivir, molnupiravir, and nirmatrelvir-ritonavir, have become integral to managing SARS-CoV-2 infection, particularly in high-risk populations (Singh et al., 2022). Although the bulk of allergy literature has focused on vaccine-related hypersensitivity (Maki et al., 2021; Sengupta et al., 2023), emerging reports indicate that allergic reactions to antiviral drugs, while uncommon, can occur and range from mild cutaneous eruptions to severe anaphylaxis (Reactions Weekly, 2023).
The pathophysiology of these reactions may involve IgE-mediated hypersensitivity or non-IgE-mediated mechanisms, including pseudo-allergic responses (DE WECK et al., 1986). Clinical presentations typically manifest within minutes to hours of drug administration but can also be delayed. Diagnosis is complicated by overlapping symptoms with COVID-19 itself and other comorbidities.
Current recommendations for managing suspected antiviral drug allergies are extrapolated from general principles in drug hypersensitivity management and vaccine allergy protocols (Maki et al., 2021). Skin testing and graded drug challenges, while not yet standardized for COVID-19 antivirals, have been proposed as tools to confirm or exclude allergy in ambiguous cases. Desensitization protocols may be considered when antiviral therapy is essential and no alternatives exist, although data specific to COVID-19 antivirals are lacking.
Natural adjunctive therapies have been explored to mitigate COVID-19 symptoms and reduce reliance on antivirals, but their role in preventing or managing allergic reactions to antivirals is unproven (Ozdemir et al., 2022).
Caveats and uncertainty
The evidence base for allergic reactions to COVID-19 antiviral therapies remains limited and largely anecdotal. Most data derive from case reports, pharmacovigilance databases, or extrapolation from vaccine allergy literature rather than prospective studies or randomized trials. The novelty of these agents means that standardized diagnostic algorithms, validated skin test reagents, and desensitization protocols are not yet established.
Confounding factors such as concurrent medications, underlying COVID-19 symptoms, and comorbid allergic conditions complicate the attribution of reactions solely to antivirals. Moreover, the heterogeneity of antiviral agents with differing molecular structures and excipients may influence allergenicity, but comparative data are lacking.
Finally, the risk-benefit assessment for continuing antiviral therapy in patients with suspected allergy must consider the severity of COVID-19, alternative treatment options, and patient-specific factors, underscoring the need for individualized clinical judgment.
How this may change practice
Allergy clinicians should be aware of the potential for allergic reactions to COVID-19 antiviral therapies and incorporate this consideration into their differential diagnosis when evaluating adverse events in treated patients. Early recognition and appropriate management of hypersensitivity reactions can improve patient safety and treatment outcomes.
Development and dissemination of standardized protocols for allergy testing and management specific to COVID-19 antivirals are needed. Until such guidance is available, clinicians may adapt existing frameworks from vaccine and drug allergy practice, including careful history taking, skin testing where feasible, and supervised drug challenges.
Interdisciplinary collaboration between allergists, infectious disease specialists, and pharmacists will be essential to optimize antiviral use while minimizing allergic risks. Patient education regarding signs of allergic reactions and prompt reporting is also critical.
As data accumulate, evidence-based guidelines will likely evolve, potentially expanding the role of desensitization or alternative antiviral regimens in patients with confirmed hypersensitivity.