what causes swelling under one eye

Swelling under one eye can be due to several reasons, and pinpointing the exact cause requires a bit of detective work. Possible explanations include an allergic reaction, like you suspected, or perhaps a localized infection such as a stye or conjunctivitis. Since you mentioned being bitten by something while hiking, it’s possible that’s the culprit – insect bites can lead to localized swelling and itchiness. Other possibilities include fluid retention or a slight injury that might have occurred without you noticing. Sometimes, sinus issues can also affect the area under the eyes, but these often affect both sides unless the infection is significant or localized.

While stress and lack of sleep often cause puffiness, they usually affect both eyes, run out the possibility that your sleeping habits are solely to blame for this. Assess if you’ve been exposed to any new products, like creams or cosmetics, that might have caused an allergic reaction. Though you’re not experiencing severe symptoms like pain or redness, I recommend you still watch for any sign of infection like an increase in swelling, redness, warmth, or pain around the area. If any of these occur, or if the swelling worsens, it would be wise to consult a doctor to rule out more serious conditions. In the mean time, try to reduce swelling by using a cold compress and elevating your head while sleeping, which can help reduce fluid retention. Avoid rubbing or touching the area to minimize irritation and possibly, consult with your primary care once you can, especially if this doesn’t improve over the next few days or if you spot new symptoms.