There’s nothing like a where-did-this-come-from type of skin rash to throw you for a loop. No idea what’s causing those raised, itchy bumps and splotches? That’s not entirely surprising. Skin rashes, after all, can have many different shapes, sizes, and colors—and they have many possible causes too.
Often, though, a rash can point to an allergic reaction, which occurs when your immune system overreacts to a certain substance. Allergies are no joke—when left unchecked, they can snowball into more serious health complications. Of course, allergies can cause a huge variety of symptoms, but a skin rash might be the first sign that something is up.
How can you tell if your skin rash might be an allergic reaction? The best way to know for sure is to visit a doctor, but until then you can keep an eye out for the most common symptoms. Ahead, learn about the signs you should keep on your radar.
Why do allergic reactions sometimes manifest as skin rashes?
Here’s the thing: The link between allergies and skin rashes depends on the type of allergic reaction you’re dealing with. Different allergens cause symptoms in different ways.
Sometimes, allergy-induced skin rashes are caused by eating certain foods, Benjamin Ungar, MD, assistant professor of dermatology at the Icahn School of Medicine at Mount Sinai, tells SELF. This involves a classic immediate allergic reaction.
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A quick explainer: Your immune system’s job is to protect you from potentially harmful microorganisms (like bacteria and viruses); it’s your body’s first line of defense. But sometimes, those immune cells mistake typically benign substances, like food, as a threat. This sparks a false alarm, causing those cells to attack the “invaders” and produce antibodies called immunoglobulin (IgE), according to the American Academy of Allergy Asthma & Immunology (AAAAI). These antibodies trigger the release of chemicals, one of which is called histamine, causing allergy symptoms that develop soon after eating the offending food, according to a 2021 study published in Cells.1 Histamine can affect many areas of the body, including the lungs, digestive tract, heart, and skin. Most people with food allergies will experience multiple symptoms, but when hives are involved (a common type of skin rash in allergic reactions), it’s because histamine is released in the skin cells, which triggers a chain reaction that ultimately ends with inflammation and swelling.
In most cases, skin rashes caused by allergies are related to contact with external allergens, Dr. Ungar explains. In other words, the rash develops when your skin touches a substance in your environment, like nickel or fragrances in cosmetics.2 This is known as allergic contact dermatitis and involves localized symptoms that take longer to develop—about 48 to 96 hours, Sebastian Lighvani, MD, an allergist at Lenox Hill Hospital in New York City, tells SELF. Unlike classic food allergies, contact dermatitis does not involve IgE antibodies, but it does involve a response of immune cells in the skin, Dr. Lighvani says.
What are signs your skin rash might be an allergic reaction?
An allergic reaction can manifest as a skin rash in myriad ways. It depends on many factors, including the cause and severity of your reaction. And in the case of contact dermatitis, the length of the contact matters too.2 Needless to say, the symptoms can look different for everyone and may include:
1. Itchiness
Most rashes are itchy, including those caused by food allergies and allergic contact dermatitis. In fact, when it comes to allergy-induced skin rashes, itching is often the main symptom, Dr. Ungar says. It might even be what made you first notice the rash.
Source: SELF
