When your body is injured or stressed, it releases additional histamine to the affected area. This increases blood flow to that area and assists with healing. However, it also can trigger an itching sensation.You may find relief with an over-the-counter antihistamine drug. The brand doesn't particularly matter, but you may want to try more than one as you may find one is more effective for you than others. Keep in mind that some antihistamines, such as Benadryl, may cause drowsiness, and this may be unsafe for running since you need to be alert.Never take more than the recommended dose or more than one antihistamine at a time, as it could cause drowsiness and other side effects. Take your antihistamine about a half hour before you plan to go for your run.
If you find that over-the-counter antihistamines reduce, but don't eliminate, your itching, you may want to talk to your doctor about getting a stronger drug in prescription form.
 You lose a lot of moisture through your breath, as well as through sweating. Particularly in the drier air of winter, your itching may be a result of dehydration because you're not drinking enough water.Being dehydrated may contribute to your body's production of histamine, which could be the cause of your itching – especially if you don't have this problem during the warmer months or when you're running indoors on a treadmill.
In cold weather, you may not feel much like drinking water. You don't necessarily want ice water (which will have a cooling effect on your body), but you do want to drink a glass of water 30 to 45 minutes before you go out running, and another when you're done with your run.
If feasible, you also want to have a water bottle with you so you can drink water during your run – especially if you're running on a treadmill or going a long distance.
 If your itching is accompanied by redness, hives, or lesions, you may have exercise-induced urticaria. This is an allergic reaction triggered by exercise and typically controllable with medication.If you have a history of breaking out in hives in response to stress or anxiety, you may be more likely to have this condition.
Talk to your physician or to an allergy specialist if you believe you have exercise-induced urticaria. As this is a relatively uncommon condition, you may have to talk to several professionals before you get the help you need.
 If your itching persists for more than four to six weeks and does not respond to over-the-counter antihistamines, or is accompanied by other symptoms, you may have a more serious medical condition.Gather information before your appointment, so you're prepared to answer your doctor's questions. You may want to measure your heart rate after 10 minutes or so of running, and take note of normal conditions when you go on a run.
Be sure to tell your doctor of any acute causes, such as dry skin or a reaction to your detergent or fabric softener, that you believe you've eliminated.
Keep in mind that finding relief for your symptoms still may involve a bit of trial and error as your doctor finds the right prescription or other treatment that will work for you.
Take a non-drowsy antihistamine.
Stay hydrated.
Check for welts or rashes.
Consult your physician.
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