Sunburn makes you feel cold because your body launches an inflammatory response that resets your internal thermostat. The same immune signals that cause redness and swelling also travel to your brain and trick it into thinking your body is too cold, triggering chills and shivering even though your skin is radiating heat. Several overlapping mechanisms drive this sensation, and understanding them helps explain why a bad sunburn can leave you reaching for a blanket on a warm day.
Your Immune System Triggers a Fake Fever
When UV radiation damages skin cells, your immune system responds much the way it would to an infection. Damaged cells release inflammatory signaling molecules called cytokines, including interleukin-1 beta, a compound that kickstarts the body’s acute-phase response. These cytokines circulate through your bloodstream and eventually reach the brain’s temperature control center, a small region called the preoptic area that acts like your body’s thermostat.
Once inflammatory signals reach the brain, they prompt the production of a chemical messenger that effectively turns up the thermostat’s set point. Your brain now “believes” your normal body temperature is too low. To close that gap, it initiates the same warming behaviors you’d experience with a flu: shivering, goosebumps, and an overwhelming urge to bundle up. Research has shown this process works through two brain pathways simultaneously. One drives automatic responses like shivering and constricting blood vessels near the skin. The other acts on emotional circuits tied to discomfort, which is why chills feel so unpleasant and make you instinctively seek warmth.
This is the same mechanism behind fever chills during illness. Your actual body temperature may be rising, but because the thermostat has been reset higher, you perceive your current temperature as cold. With a moderate to severe sunburn, the inflammatory load can be significant enough to produce a low-grade fever alongside that chilly feeling.
Damaged Skin Loses Heat Faster
Healthy skin is a remarkably effective barrier against water and heat loss. Sunburned skin is not. When UV radiation damages the outermost layer of your skin, it compromises this barrier, and water begins evaporating through the surface much faster than normal. Measurements of water loss through damaged skin show rates roughly ten times higher than through intact skin. As that moisture evaporates, it pulls heat away from your body, the same cooling principle behind sweating, except now it’s happening continuously and without your body’s control.
This accelerated evaporation does two things. It cools the skin surface, contributing to that cold sensation, and it drains fluid from your body. Even a 1% drop in body weight from water loss places measurable stress on your cardiovascular system, raises your heart rate, and impairs your body’s ability to regulate its own temperature. The result is a feedback loop: damaged skin loses water faster, dehydration makes temperature regulation harder, and your body struggles to find equilibrium.
Blood Flow Shifts Away From Your Core
Sunburned skin turns red because blood vessels near the surface dilate dramatically as part of the inflammatory response. This increased blood flow is your body’s way of delivering immune cells to the damaged area and beginning repairs. But it comes with a thermal cost. When large volumes of warm blood flow to the skin surface, that heat radiates outward into the surrounding air. Essentially, your body is pumping its warmth to the surface and losing it to the environment through convection.
If your sunburn covers a large area, like your entire back or chest, this redistribution of blood can meaningfully lower your core temperature. Your internal organs and muscles get less warm blood, and your brain registers the drop. Combined with the thermostat reset from inflammation, this creates a pronounced sensation of being cold from the inside out, even while your skin feels hot to the touch.
Why Severe Sunburn Feels Like Being Sick
The chills are just one part of a broader systemic response. Severe sunburn can produce headache, nausea, fatigue, and fever, a cluster of symptoms sometimes called sun poisoning. This isn’t a separate condition so much as a sunburn intense enough to trigger a body-wide inflammatory reaction. The same cytokines responsible for your chills also cause that general feeling of malaise, the “hit by a truck” sensation familiar to anyone who’s had a bad flu.
A fever above 103°F (39.4°C) with vomiting, signs of dehydration like dizziness or faintness, or large blisters on the face, hands, or genitals all signal a sunburn that needs medical attention. Confusion, worsening pain despite home care, or cold and clammy skin are also warning signs that the body’s inflammatory response has escalated beyond what rest and fluids can manage.
What Actually Helps
The chills will resolve as the inflammation subsides, which typically takes one to three days for a moderate sunburn. In the meantime, the most effective things you can do address the root causes directly.
- Hydrate aggressively. Your damaged skin is losing water at an accelerated rate, and dehydration makes temperature regulation worse. Drink extra water for at least 24 hours after a significant burn.
- Cool the skin in short intervals. A clean towel dampened with cool water, applied for about 10 minutes several times a day, helps reduce inflammation without shocking your system. Cool baths with a small amount of baking soda (about 2 ounces per tub) can also soothe large areas.
- Warm your core, not your skin. If you’re shivering, it’s fine to use a light blanket or wear loose clothing. Your brain is telling you you’re cold, and fighting that signal just makes you miserable. Avoid anything that traps heat against the burned skin itself, though, as that can worsen inflammation.
- Take an anti-inflammatory. Over-the-counter options like ibuprofen can help lower the inflammatory signaling that’s resetting your thermostat, easing both the chills and the pain.
The paradox of sunburn, feeling cold while your skin is on fire, makes perfect sense once you understand it as an immune response rather than a temperature problem. Your body is reacting to tissue damage the same way it reacts to an invading pathogen: by turning up the thermostat, mobilizing resources, and making you feel lousy enough to rest while it handles repairs.