Can Someone Suddenly Become Allergic to a Substance?

Can someone who was previously not allergic to a substance suddenly become allergic? The answer is yes, and this phenomenon is especially notable in adult-onset food allergies.

The Mechanism of Sudden Allergies

Allergies develop after a person's immune system gains exposure to an allergen. You aren't allergic until you are exposed to the allergen for the second time. Therefore, the first exposure does not result in an allergic reaction. However, the second exposure can trigger an allergic reaction, which might be quite severe. For instance, adult-onset food allergies can manifest in this manner, where an individual has been consuming a food item for years without any issues, only to suddenly experience an allergic reaction upon subsequent exposure.

My personal experience with milk products highlights this process. For months, I had hives on my upper legs, but I couldn't identify the cause. Different places on my legs on different days, but they persisted almost always. Antihistamines alleviated the symptoms temporarily, and the allergist was unable to pinpoint the source. One day, after consuming eggs and cheese, I began feeling 'iffy.' After drinking Benadryl, I felt better for a brief while. However, three hours later, the symptoms worsened, and despite taking another dose of Benadryl, I couldn't stand up and felt extremely faint and dizzy. I administered an EpiPen and dialed 911 for emergency assistance.

Once I cut all milk products from my diet, the hives disappeared. Before this change, I had been consuming milk or cheese daily, often more than once a day, and the hives were a constant presence.

Multiple Sudden-Onset Allergies

After this experience, I developed several more allergies, all of which were sudden. However, I was more vigilant about detecting hives as a sign of an allergic reaction. I was diagnosed with numerous adult sudden-onset IgE-mediated allergies, all confirmed by a board-certified allergist in 2011. These allergies have significantly impacted my life and restrict my diet so much that I've been diagnosed with malnutrition.

The restrictions imposed by IgE-mediated allergens have become such that many of them are exempt from FDA labeling requirements. This has left me feeling extremely cautious about what I eat, adding another layer of anxiety to my everyday experience.

Nonspecific Sudden Rashes

It's not just food allergies that can develop suddenly. Years ago, I developed a rash all over my body with no apparent cause. The doctor and I were equally perplexed. The rash cleared up within 24 hours and has never returned.

Overall, the development of sudden allergies can be both perplexing and life-altering. Understanding the mechanisms behind these allergic reactions can help individuals be better prepared for such sudden changes in their health.