Abstract
BACKGROUND: Several population studies demonstrated an increased risk of allergic rhinitis in patients exposed to acetaminophen. However, no histologic studies have been conducted to assess the relationship between acetaminophen exposure and allergic rhinitis. OBJECTIVE: In this study, we investigated the association between chronic acetaminophen exposure and the development of allergic rhinitis in a rat model. METHODS: Ten female Sprague-Dawley rats were randomly assigned to either a control (n = 5) or an acetaminophen group (n = 5). The acetaminophen group received 200 mg/kg/day of acetaminophen suspended in yogurt via oral gavage for 120 days. The control group received only the yogurt vehicle. Allergic behavioral responses, including nose rub, eye rub, ear scratching, and neck and/or face scratching, were quantified. The rats were killed, and the noses were harvested. The portion of the nose, including the nasal septum and the inferior turbinates, was embedded in paraffin, sectioned, and stained with hematoxylin and eosin to quantify the inflammatory infiltrate. RESULTS: The average number of allergic responses per animal was 13.2 in the acetaminophen group versus 6.2 in the control group (p = 0.032). All the rats in the acetaminophen group (100%) had mast cells infiltrating the lamina propria of the inferior turbinate, whereas mast cells were detected in only 40% of the animals in the control group. The average number of mast cells per animal in the acetaminophen group was 134 versus 21 in the control group (p = 0.048). CONCLUSIONS: Our study was the first to demonstrate a histologic association between chronic exposure to acetaminophen and rhinitis. Further research to elucidate the mechanism that underlies these findings is necessary.