Cotton fever typically lasts 12 to 48 hours, with most episodes resolving within 24 hours. It’s a self-limited reaction that comes on fast and feels severe but usually passes on its own without lasting harm.
What Cotton Fever Is
Cotton fever is a systemic inflammatory reaction that happens after injecting drugs filtered through cotton. The cotton can harbor a bacterium called Pantoea agglomerans, which produces endotoxins. When those endotoxins enter the bloodstream, the body mounts an intense immune response that mimics a serious infection. It occurs in up to 54% of people who inject drugs, making it remarkably common in that population.
The reaction is not a true bloodstream infection. There’s no documented bacteremia in a typical cotton fever episode, meaning the bacteria themselves aren’t multiplying in your blood. Your body is reacting to the toxins they left behind, which is why the whole thing burns out relatively quickly once your immune system clears them.
How Quickly Symptoms Start
Symptoms usually appear within 15 to 30 minutes after injecting, though they can take up to an hour. The onset is rapid enough that most people can connect it directly to a specific injection. This fast timeline is one of the things that distinguishes cotton fever from a more serious infection, which tends to develop over hours or days rather than minutes.
What It Feels Like
Cotton fever hits like a sudden, intense flu. The hallmark symptoms are high fever, shaking chills, and a racing heart. In documented cases, temperatures around 100.5°F with heart rates above 120 beats per minute are typical. Blood pressure can drop, and breathing may feel faster than normal. Many people also experience headache, nausea, muscle aches, and general misery that feels disproportionate to what’s actually happening in the body.
The severity of symptoms is part of what makes cotton fever frightening. It can feel like something is seriously wrong, and in some cases, something is. The challenge is that the early presentation looks nearly identical to sepsis or other dangerous bloodstream infections.
When It Might Be Something Worse
The biggest risk with cotton fever isn’t the condition itself. It’s assuming that every post-injection fever is “just” cotton fever when it could be septic shock or another life-threatening infection. True cotton fever resolves within 12 to 48 hours without antibiotics. If symptoms persist beyond that window, worsen after initially improving, or include confusion, extreme weakness, or skin changes, the situation may be more serious.
There is also a small but real connection to heart valve infections. Cotton fever occurs in a large percentage of people who inject drugs, yet only two published case reports have linked it to endocarditis (infection of the heart valves). That’s a low number, but some researchers believe cotton fever could be an unrecognized risk factor for this complication, particularly with repeated episodes over time. Endocarditis develops slowly and can cause lasting damage, so recurring fevers after injection deserve medical attention even if prior episodes resolved on their own.
Managing Symptoms at Home
Because cotton fever is self-limiting, treatment is supportive. Staying hydrated is the most important thing you can do. The fever and sweating can drain fluids quickly, and dehydration will make you feel significantly worse. Over-the-counter fever reducers like ibuprofen or acetaminophen can help bring the temperature down and ease body aches. Rest, blankets for the chills, and small sips of water or electrolyte drinks are the basics.
The hard part is waiting it out. Most people feel noticeably better within 12 hours, and the vast majority are back to baseline within 24. If you’re still running a fever or feeling worse after 48 hours, that timeline no longer fits the pattern of cotton fever, and you should seek medical care.
Reducing the Risk
Cotton fever is directly tied to reusing cotton filters or using cotton that has been sitting out. Bacteria colonize the cotton after it’s been used, and the longer it sits, the more endotoxin accumulates. The most effective way to prevent cotton fever is to use a fresh filter for every injection and never reuse or share cotton. Avoiding “cotton shots,” where residual drugs are extracted from previously used filters, eliminates the primary source of exposure. Syringe service programs in many areas provide sterile filters and supplies specifically to reduce risks like this.