The signs of an allergic reaction to vitamin D often include asthma symptoms and other common allergy signs, such as itchy eyes and a runny nose. An individual may also develop a condition that affects the skin, such as hives, rashes, or eczema, because of this type of allergy. Additionally, an affected person could suffer a severe reaction that includes facial or throat swelling, lowered blood pressure, extreme difficulty breathing, and dizziness or fainting.

The most common signs of an allergic reaction to vitamin D are those that involve the respiratory system. Often, an individual with this type of allergy develops asthmatic symptoms upon exposure. For example, he may wheeze, develop labored breathing, and notice that his chest feels unusually tight. Shortness of breath and chest pain are also associated with this type of allergic reaction. Such symptoms can develop even in people who do not have a history of asthma.

Some people develop signs of hay fever when they have an allergic reaction to vitamin D. For example, an affected person may develop itchy eyes and a runny nose or experience nasal congestion. Some people also develop itching in odd places, such as the ears and throat, as a result of this type of allergy. Coughing and post-nasal drip may become problems as well. Additionally, some might notice a buildup of uncomfortable pressure in their sinuses as a result of a vitamin D allergy.

In some cases, an allergic reaction to vitamin D causes signs to develop on a person's skin. For example, this type of reaction can cause hives or itchy rashes to develop as well as redness and inflammation. This type of allergy may also contribute to the development of skin conditions that are often associated with allergies, such as eczema. This chronic skin condition is marked by dry areas of skin that can appear scaly or leather-like. In some cases, skin affected by eczema will develop burning sensations, ooze fluid, or bleed as well.

Sometimes a person suffers a severe allergic reaction to vitamin D that can prove life threatening. This type of reaction often is accompanied by such symptoms as throat, mouth, or face swelling; hives; difficulty breathing; and heart rate changes. In some cases, a person may also experience dizziness, fainting, or a significantly lowered blood pressure. Any allergic reaction to vitamin D may warrant a doctor's evaluation, but a severe reaction usually requires emergency medical attention.