18 Hidden Causes of High Neutrophil Counts That Doctors Want You to Know

12. High-Altitude Exposure

People who travel to or live at high altitudes may experience a condition known as altitude-induced neutrophilia. At higher elevations, oxygen levels decrease, which triggers a physiological response in the body to compensate. One of these responses includes an increase in red blood cell production to carry more oxygen. However, studies have also shown that white blood cell counts, particularly neutrophils, tend to rise in individuals exposed to high altitudes for extended periods. This is believed to be due to mild, sustained hypoxia (low oxygen levels), which places stress on the body and stimulates the bone marrow to produce more neutrophils. In some cases, this effect can persist for weeks or months after prolonged high-altitude exposure, especially in climbers, hikers, and residents of mountainous regions. While generally not harmful on its own, altitude-related neutrophilia is an intriguing example of how environmental factors can influence immune function.