Study Reveals Antihistamines May Hinder Fitness Gains During Exercise

A recent study published in the *Journal of Applied Physiology* on May 30, 2025, reveals a significant relationship between the use of antihistamines and fitness performance among individuals engaging in regular exercise. Conducted by researchers at the University of Oregon, this study highlights that taking antihistamines before workouts can substantially reduce fitness gains, particularly during aerobic activities.

The study involved 16 participants who followed a structured biking regimen over six weeks, during which they cycled three to four times per week. Participants were divided into two groups; one received antihistamines prior to each training session while the other was given a placebo. The results showed that those who took the placebo exhibited almost double the performance improvement compared to their antihistamine counterparts. Specifically, the placebo group demonstrated significantly greater enhancements in muscle blood flow and overall fitness levels.

John Halliwill, a professor of human physiology at the University of Oregon and a co-author of the study, emphasized the critical role histamine plays in exercise adaptation. He noted, “In exercise, it actually seems to be playing a very similar role of facilitating our adaptation to stress.” This indicates that histamine not only contributes to allergy responses but is also crucial for optimizing exercise capacity and recovery.

Histamine functions by enhancing blood circulation, which is essential for delivering nutrients and oxygen to muscles during physical activities. The findings suggest that high levels of antihistamine can interfere with these physiological processes, thus diminishing the potential benefits of regular exercise.

The study's implications extend beyond mere performance metrics; they raise important questions about how individuals manage allergies without compromising their fitness goals. As seasonal allergies affect many individuals, especially during spring and fall, the temptation to use antihistamines for symptom relief before workouts is common. However, the research encourages a reevaluation of this practice, especially for those serious about their fitness outcomes.

Health experts recommend that individuals experiencing allergy symptoms consult healthcare providers to explore alternative strategies that do not impede physical performance. As Professor Halliwill advises, “Understanding the complex interaction between histamine and exercise can guide better management of both allergies and fitness routines.”

This research contributes to the growing body of evidence surrounding the interactions between medication and physical performance, urging both individuals and healthcare professionals to consider the broader implications of medication usage in athletic contexts.

In conclusion, while antihistamines may provide immediate relief from allergy symptoms, their potential impact on fitness gains cannot be overlooked. Future research is necessary to explore alternative treatments for allergies that align better with exercise performance, allowing individuals to prioritize both health and fitness simultaneously.