Some allergies cause nosebleeds, although not always directly. Allergies that dry the inside the nose, irritate your sinuses or make you rub your nose can all lead to nosebleeds. Most of the time, nosebleeds don't last long and don't cause any serious health problems. However, if your bleeding persists after 20 minutes or you find blood in your mouth coughed up from your lungs, speak to a doctor as soon as possible.
The inside of your nose back to your throat is lined with soft tissue. This tissue has many tiny blood capillaries. In normal circumstances, this lining is moist and easily allows air to pass through. However, allergies can trigger inflammation much like the congestion felt from a cold. When that happens, your nasal passages become more sensitive and dry. This makes it more likely that you'll get a nosebleed, according to the NYU Langone Medical Center. For example, rubbing your nose, coughing or blowing into a tissue too hard could all trigger a nosebleed when allergies cause inflammation.
One form of allergic reaction commonly associated with nosebleeds is allergic rhinitis. This happens when you're allergic to an airborne particle, such as pollen, cut grass, dust or pet hair. Breathing it in might make your eyes stream and your nose itch. Persistent coughing, sneezing or wheezing can irritate the sinuses and the nasal tissue. These often cause bleeding inside the front part of the nose. Your doctor may prescribe antihistamines or a nasal spray to combat allergic rhinitis.
You can treat nosebleeds caused by allergic reactions in much the same way as nosebleeds caused by a cold. In general, when your nose bleeds, you need to sit and lean forward. Gently pinching shut your nostrils without moving your fingers around stops the flow. Hold for 10 minutes. If you're able, put a bag of frozen peas or crushed ice against your nose. This helps to slow the flow of blood to the nasal lining and reduce swelling.
Some allergy medication dries out the lining of the nose, according to Ohio State University Student Health Services. This includes nasal sprays and medication in pill form. Although your allergies might not immediately trigger a nosebleed, the drying of your nasal passages from medication can cause bleeding. If you regularly experience nosebleeds but aren't sure of the cause, your doctor can perform an allergy test on you. This helps isolate potential allergens that might trigger a reaction, such as dust or pet hair.