Does Vitamin C Help With Allergies or Make Them Worse?

Vitamin C is known for boosting your immune system. Vitamin C can help allergies because a mere two grams of vitamin C can decrease histamine levels by around 38%.

Vitamin C is known for boosting your immune system. Immune cells usually protect you against harmful substances, but if the immune system overreacts and accidentally damages your own cells, it could cause allergies. Read on to learn everything you need to know about using vitamin C for allergies, its side effects, and more.

Vitamin C, also known as ascorbic acid, is a water-soluble compound. Unlike fat-soluble vitamins (e.g., vitamin A, vitamin D, vitamin E, and vitamin K), vitamin C cannot be stored in the body. This means that you need a regular supply of vitamin C through your diet or health supplements to maintain adequate levels.

Vitamin C is found in many fruits and vegetables, especially citrus fruits, yet it represents the fourth most common nutrient deficiency in the United States. Unfortunately, low levels of vitamin C can have many negative effects. For example, it could weaken your immune system. 

Allergies occur when your immune system becomes overactive in an effort to defend your body from foreign substances like pollen, dust, pet dander, and food proteins. These substances are called allergens. 

The symptoms of an allergic reaction include itching, rashes, runny noses, red or watery eyes, sneezing, swelling, difficulty breathing (asthma), vomiting, diarrhea, and dangerous airway swelling (anaphylaxis) in severe cases.

Your allergy symptoms occur due to a chemical referred to as histamine, which is produced by specialized immune cells called mast cells. These cells become activated when they come into contact with allergens. At that point, they start secreting histamine, culminating in an allergic reaction.

Vitamin C has natural antioxidant and antihistaminic properties, though, so it can decrease inflammation, swelling, and allergy-related symptoms.

Antihistamine medications are available for seasonal or mild allergies. However, all of these medications have side effects. 

Unlike these medications, vitamin C is a natural substance. Instead of blocking histamine receptors, it reduces the amount of histamine produced by your body. A mere two grams of vitamin C can decrease histamine levels by around 38%.

Higher doses of vitamin C taken intravenously (IV) might be even more effective. In a study of 89 people who received an IV infusion of 7.5 grams of vitamin C, blood histamine levels decreased by about 50%.

These effects are more prominent among people who have allergies, though, compared with those who have infections. In another observational study, IV vitamin C was able to minimize allergy symptoms in 97% of participants, and only one person experienced side effects.

Meanwhile, among 60 people who used a vitamin C nasal spray, 74% reported an improvement in their allergy symptoms like runny nose and sneezing.

Large-scale human studies are needed to confirm these findings, however.

Vitamin C seems most suitable to deal with symptoms related to the nose, mouth, and throat (i.e., upper respiratory tract), which are usually caused by seasonal or environmental allergies. Some common environmental allergens include mold, dust, pet dander, and pollen.

These allergens usually trigger a histamine reaction in the nose or lungs. If they affect the nose, they could cause allergic rhinitis. The symptoms of this condition include a runny nose, sneezing, red and watery eyes, and nasal congestion (i.e., the feeling of a blocked nose).

If they affect the lungs, they could cause asthma. The symptoms of asthma include wheezing (i.e., making a squeaky sound while breathing), shortness of breath, chest tightness, and coughing.

The antihistaminic properties of vitamin C can help control the symptoms of allergic rhinitis and asthma. This is because vitamin C can suppress the activity of the histamine-producing mast cells in the lungs. The antioxidant properties of vitamin C may also protect the lungs from oxidative damage caused by harmful free radicals.

However, the effect of vitamin C on food allergies has yet to be studied. Food allergies can be quite severe and can even become life-threatening if not treated on time. Vitamin C is not recommended in such cases. Consult your healthcare provider immediately if you experience any food allergy symptoms, even if they’re mild. 

According to the National Institutes of Health, the recommended daily amount of vitamin C for men is 90 milligrams per day, and for women, it is 75 milligrams per day. However, pregnant and breastfeeding women require around 85 milligrams and 120 milligrams of vitamin C per day, respectively.

To treat health conditions like allergic rhinitis, most health care professionals recommended a vitamin C dosage of up to 2 grams per day for adults and less for children. Because your body cannot store vitamin C and eliminates the excess amounts in your urine, it’s unlikely that you will experience vitamin C toxicity, but in some cases, high doses (e.g., 2 grams) have been linked to side effects like nausea, vomiting, and diarrhea. This is because your gut has a limited capacity to absorb vitamin C. The excess amounts that remain unabsorbed could have a laxative effect on the gastrointestinal cells.

Hence, the upper limit of vitamin C dosage has been set at 2,000 milligrams (i.e., 2 grams). If you’re concerned about side effects, don’t take such high doses immediately. Start with smaller doses and gradually build up if you don’t experience any negative effects. You could also split up your dosage into multiple small doses taken throughout the day.

Another way that healthcare professionals bypass vitamin C absorption limits is by giving patients IV infusions of vitamin C. When vitamin C is administered in this manner, it directly enters your bloodstream and can act without first needing to be absorbed. Thus, healthcare providers use IV vitamin C to administer very high doses safely without triggering any side effects.