Stress & Parasites When cortisol stays high for too long, it slows stomach acid. Less acid means some parasites that would normally be neutralized survive. Stress also dampens the gut’s immune lining (secretory IgA), which usually keeps invaders in check. Your gut’s defenses are on low power, giving existing parasites a chance to multiply. Chronic stress also tweaks immune signaling. Your body’s usual “attack and clear” commands become miscommunicated. At the same time, gut m