You are most likely having an allergic reaction to an unspecified allergen when this takes place. If this only occurs 2 times a year and during the summer months.
You can take an over the counter allergy medication such as Benadryl or Claritin-D to speed the reduction of the swelling when this happens. However, you may notice that your mouth, nose and eyes become dry from this. The good thing is this is only temporary while you are taking the medication. You can also hold a cool washcloth over your face for 5 minutes every hour. This will also reduce the swelling.
This could also be a reaction to medications that you are taking. Some medications can produce symptoms if the person that takes them is overexposed to the sun. If you are currently taking medications, you shouuld ask your pharmacist or doctor about this. If this isn't the problem and you begin to notice that this is occuring more frequently or additional symptoms are occuring with this,then you should see a doctor. You may have developed allergies and if so your doctor will provide treatment or refer you to an allergist. If the swelling is due to heat he will advise you of ways to avoid this or examine for further reasons.
If this information has been helpful, then please do accept. Positive feedback is also appreciated. If I can help you further let me know.
Thank You,
Terri L. Romaker