Eaten a Known Allergen, Now What?

Imagine biting into a seemingly delicious sandwich only to be hit by an unfamiliar “creamy” taste you’ve never experienced before…“Is this what cheese tastes like?” 😲

As someone with a milk allergy, I’ve experienced this sinking realization many times, feeling helpless for the impending allergic reaction. Over the years, I’ve learned you can’t predict allergic reactions, but with diligence, you can minimize the damage they cause.

As a resident doctor working in the UK and someone with food allergies since childhood, I’ve experienced allergies from both a personal and medical perspective. This guide, along with a calm, measured approach, will help you prepare for the best- and worst-case scenarios to keep you as safe as possible when navigating food-related allergic reactions.

Assessing the Severity of a Reaction

First, it’s vital to recognize the signs of an allergic reaction. Unfortunately, there's no one-size-fits-all way to predict how intense a reaction might be. Reaction severity varies from person to person and depends on factors like stress, medication, and even time of day. Generally, allergic reactions are divided into mild to moderate or severe categories, depending on symptoms and signs:

• Mild to moderate reactions involve symptoms affecting only one area of the body. For example, itching, mild swelling, or a scratchy throat. These can often be managed with antihistamines and only require emergency medical intervention if symptoms escalate.

• Severe reactions (anaphylaxis) involve the respiratory or circulatory systems and may include shortness of breath, wheezing, throat tightness, persistent dizziness, or collapse. Significant swelling of the lips or tongue also affects the respiratory system, as it can block the airway. These reactions are life-threatening and require immediate administration of adrenaline (also known as epinephrine) and emergency medical care.

The Role of Antihistamines: Your First Line of Defense

So, what role do antihistamines play in mitigating mild allergic reactions? When your body encounters an allergen, it produces a substance called histamine, which makes your blood vessels expand and leak. This causes redness, swelling, itching, and a variety of other “allergy” symptoms. Antihistamines (e.g., Zyrtec or the generic version, cetirizine) block histamine from causing these effects, reducing the severity of the allergic response. Think of antihistamines as “fire extinguishers.” They work best when the histamine “fire” is small and easy to control. Therefore, it’s important to take antihistamines when you first notice symptoms, as this is when they’re most effective.

The Role of Epinephrine: The Life Saver

If antihistamines are the fire extinguishers, epinephrine is the “fire department” arriving with a full firefighting crew and equipment. This is because epinephrine is the only medication that can reverse the symptoms of anaphylaxis. It constricts the blood vessels to reduce swelling, relaxes airway muscles to ease breathing, and increases blood pressure. It’s the most important medication to treat allergic reactions, so when in doubt, use epinephrine! The benefits always outweigh the risks.

For a deep dive on epinephrine, check out this blog post.

Preparing an Emergency Food Allergy Kit

We know what we need to manage allergic reactions, so let’s build our emergency allergy kit. This kit should be tailored to your specific needs, but should generally include:

• Antihistamines (e.g., Zyrtec or Benadryl)

• Epinephrine (e.g., EpiPen or Neffy)

• A medical ID bracelet and/or card with food allergy details

• A food allergy action plan or instructions for recognizing allergic reactions and using medications

It’s important to keep this kit accessible, whether you're at home, work, or traveling. When I’m on a trip, I keep my kit with my travel money and print instructions in the local language. It’s also helpful to tell friends, family, and colleagues where you keep your kit in case you need them to retrieve it.

Now that we’ve defined the differences in the severity of allergic reactions and the role of medications, the next step is developing an “Allergy Action Plan” to use in the event of accidentally ingesting an allergen. Having a set protocol, devised with the help of your provider, is crucial during emergencies when it can be hard to think straight. Here’s a good example of what this might look like.

Allergy Action Plan

1. Stop Eating and Assess

1. If there is any doubt over the safety of the food, stop eating it immediately.

2. For mild symptoms—like an itchy throat, redness, or mild swelling—take an antihistamine immediately. If you vomit after taking the antihistamine, take another. If your symptoms worsen, proceed to step 7.

2. Tell Someone

1. Symptoms can escalate rapidly into anaphylaxis. It’s important to tell someone you’re having an allergic reaction so they can help, if needed.

3. Prepare for Escalation

1. Locate your epinephrine in case it’s needed.

4. Go to the Bathroom with Someone

1. Allergic reactions can involve gastrointestinal symptoms like diarrhea and vomiting. Have someone go with you to prevent isolating yourself in case you need help during the reaction. Do not take anti-diarrhea medication, as it's best for the body to flush out the allergen.

5. Stay Hydrated

1. Keep yourself hydrated, especially if you’re experiencing symptoms like diarrhea or vomiting.

6. Reassess Symptoms

1. Continuously reassess for symptoms like throat swelling or difficulty breathing.

7. If in Doubt, Use Epinephrine

   1. If there are any ‘severe’ symptoms or concerns of worsening symptoms:

      1. If using epinephrine with a needle, lie flat on your back with your legs elevated. If using needleless epinephrine, sit comfortably.

      2. Administer epinephrine.

      3. Dial 911 stating “Anaphylaxis.”

      4. Give another dose of epinephrine if symptoms persist or worsen. They come in packs of two for this reason!

What to Expect in Emergency Care

If you use epinephrine or develop symptoms of a severe allergic reaction, call an ambulance immediately.

At the emergency room, medical staff will ask for a summary of what happened, what time your medication was administered, monitor your vital signs, and give additional medications. It’s normal to observe you for a few hours to ensure symptoms don’t return, as some reactions can be “biphasic,” meaning they can recur after the initial symptoms have gone away.

Post-Reaction Care

You’ve made it through the hard part! Now it’s time to debrief on what happened. It’s important to record what happened during the allergic reaction, the treatment given, and any new triggers you identified. For example, were you exercising? Did you drink any alcohol? These co-factors can combine with the effects of the allergen to increase the severity of the reaction, so it’s worth documenting to identify any patterns.

It’s also important to follow up with your healthcare provider, as they may conduct further food allergy testing or prescribe additional medications.

We all hope never to accidentally consume a food allergen. However, being prepared can make a significant difference for both your safety and peace of mind. I encourage you to review this guide and work with your doctor to develop a personalized allergy action plan. Tailor it to your specific allergies and medications, and keep it with you in your emergency allergy kit. By staying informed and prepared, you’ll be ready to face any allergic reaction, knowing how to keep yourself safe.

In the words of Maya Angelou, those of us with allergies are, “…hoping for the best, prepared for the worst, and unsurprised by anything in between.”  

— Dr. Hayley Johnson

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Dr. Hayley Johnson is a UK-based doctor and allergy advocate. With food allergies to dairy, eggs, nuts, sesame seeds, salmon, and trout, she's a seasoned expert in deciphering ingredient labels and finding creative meal alternatives. She feels strongly about allergy awareness and supporting people with food allergies to live safe, healthy, and fulfilling lives.