Allergy Medications: Antihistamines and Decongestants Risks You Can't Ignore

Dec, 5 2025

Every year, millions of people reach for antihistamines and decongestants to chase away sneezing, stuffy noses, and itchy eyes. You grab a bottle off the shelf like it’s a candy bar-no prescription, no doctor, no second thought. But here’s the truth: these common allergy meds carry real, sometimes dangerous, risks that most users never see coming.

Why Your Go-To Allergy Pill Might Be Hurting You

Antihistamines block histamine, the chemical your body releases during an allergic reaction. That’s why they stop sneezing and itching. But they don’t just stop at the nose. First-generation ones like diphenhydramine (Benadryl) and doxylamine cross into your brain. That’s why you get drowsy-50 to 60% of users do. It’s not just a side effect. It’s a safety hazard.

Think about driving after taking Benadryl. Or getting up in the middle of the night to use the bathroom and stumbling. For adults over 65, the risk of falling triples. The American Geriatrics Society calls first-gen antihistamines “potentially inappropriate” for seniors. Why? Because they don’t just make you sleepy-they cause confusion, blurry vision, dry mouth, and trouble peeing. For men with enlarged prostates, that last one can turn into a medical emergency.

Second-generation antihistamines like loratadine (Claritin) and cetirizine (Zyrtec) are better. They’re less likely to cross the blood-brain barrier. Only 10 to 15% of users feel drowsy. But even these aren’t risk-free. People with liver disease, glaucoma, or thyroid problems can still have bad reactions. And if you’re pregnant? The American College of Obstetricians and Gynecologists says stick to loratadine only under a doctor’s watch.

Decongestants: The Quick Fix That Can Backfire Hard

Decongestants like pseudoephedrine (Sudafed) and phenylephrine shrink swollen blood vessels in your nose. That’s why your nose clears up fast. But they don’t just shrink the vessels in your nose-they shrink them everywhere. Your heart beats faster. Your blood pressure spikes. That’s why people with high blood pressure are told to avoid them.

Mayo Clinic reports decongestants can raise systolic blood pressure by 5 to 10 mmHg. For someone with untreated hypertension-that’s dangerous. The CDC says over 116 million American adults have high blood pressure. Many don’t even know it. Taking Sudafed could push their pressure into stroke or heart attack territory.

Nasal sprays like oxymetazoline (Afrin) seem safer because they’re local. But use them longer than three days? You’re not helping your nose-you’re wrecking it. Half of users develop rebound congestion. Your nose gets more swollen than before. Now you’re stuck in a cycle: spray to clear it, then spray again because it’s worse. It’s not addiction-it’s pharmacology. Your body adapts, and now you need the spray just to breathe normally.

The Hidden Danger: Combination Products

You see “All-in-One Cold & Allergy” on the shelf. It promises to fix everything: runny nose, cough, fever, congestion. Sounds perfect. But here’s the catch: you’re taking three or four drugs at once. And you don’t even know it.

Many of these combos include acetaminophen (Tylenol). The FDA says the max safe daily dose is 4,000 mg. But if you’re already taking a painkiller for a headache, or a sleep aid with acetaminophen, you could easily hit 5,000 or 6,000 mg. That’s liver damage. That’s emergency room visits. In 2022, the CDC linked over 10,000 ER visits to OTC allergy meds-many from accidental overdose.

And then there’s the caffeine problem. Energy drinks. Coffee. Pre-workout powders. If you’re taking a decongestant and then chugging a Red Bull? Your heart could race out of control. The Rutgers Poison Control Center saw a 25% jump in calls from young adults mixing OTC meds with energy drinks in 2022. That’s not a coincidence. That’s a pattern.

A young adult with a pulsing heart, holding an energy drink and decongestant, surrounded by warning symbols.

When These Meds Are Absolutely Not Safe

Some people should never take these meds-not even once. The NHS and WebMD list clear red flags:

High blood pressure or heart disease
Diabetes
Enlarged prostate
Glaucoma
Thyroid problems
Liver or kidney disease
Taking antidepressants like SSRIs or MAOIs

MAOIs are especially dangerous with decongestants. The combo can trigger a hypertensive crisis-blood pressure so high it can rupture blood vessels. It’s rare, but it’s deadly. And if you’re on an MAOI, you need to wait two full weeks after stopping it before using a decongestant. Most people don’t know this.

And don’t forget kids. The FDA says no cough or cold medicine with antihistamines or decongestants for children under 2. Between 1969 and 2006, there were 123 reported deaths in young kids from these products-convulsions, heart attacks, sudden stops in breathing. Even today, 42% of OTC allergy-related ER visits involve kids under 12.

What You Should Do Instead

If you’ve been using antihistamines or decongestants for more than a week or two, you’re not treating your allergies-you’re masking them. Allergies don’t go away with pills. They need management.

For chronic congestion, nasal corticosteroid sprays like fluticasone (Flonase) are far safer than decongestants. They work slower but don’t raise blood pressure or cause rebound congestion. They’re FDA-approved for long-term use.

For mild symptoms, saline rinses or a humidifier can help. Air filters reduce allergens. Allergy shots? They’re the only treatment that actually changes your body’s response over time.

And if you’re unsure? Talk to your pharmacist. The American Pharmacists Association says 78% of OTC medication problems could be avoided with a quick chat. They know what’s in your bottle. They know what else you’re taking. They know your history. They’re not just the person who hands you the box-they’re your safety net.

An older woman with rebound congestion, surrounded by dark clouds, as a pharmacist offers a safer nasal spray.

When to Call a Doctor

Don’t wait for a crisis. Call your doctor if:

Your symptoms last more than 10 to 14 days
You feel chest tightness, rapid heartbeat, or dizziness after taking a med
You’re having trouble sleeping or feel unusually anxious
You’re over 65 and taking any antihistamine
You’re pregnant, breastfeeding, or managing a chronic condition

Dr. James Li from Mayo Clinic says it plainly: “It is always best to speak to your primary health care provider before starting new medications.” That’s not a suggestion. It’s the only smart way to use these drugs.

Over-the-counter doesn’t mean risk-free. It means you’re responsible. And if you’re not paying attention to the fine print, you’re playing Russian roulette with your health.

Can I take antihistamines every day?

Second-generation antihistamines like loratadine or cetirizine are generally safe for daily use if your allergies are persistent. But first-generation ones like diphenhydramine should never be used daily-they cause too many side effects, especially in older adults. Always check with your doctor if you need to take them long-term.

Why do decongestants raise blood pressure?

Decongestants like pseudoephedrine work by narrowing blood vessels to reduce nasal swelling. But they don’t know the difference between your nose and your heart. They tighten vessels everywhere, forcing your heart to pump harder. That increases blood pressure. For someone with hypertension, this can be dangerous enough to trigger a heart attack or stroke.

Is it safe to take decongestants with antidepressants?

No. Combining decongestants with SSRIs or MAOIs can cause a dangerous spike in blood pressure. MAOIs, in particular, can lead to a hypertensive crisis-where blood pressure rises to life-threatening levels. Even if you’re on a common antidepressant like sertraline, talk to your doctor before using any decongestant.

Can I give my child Benadryl for allergies?

The FDA warns against giving any antihistamine or decongestant to children under 2. For older children, dosing is tricky and side effects like drowsiness, agitation, or rapid heartbeat are common. Always consult a pediatrician before giving OTC allergy meds to a child-even if it’s just “one dose.”

What’s the safest antihistamine for seniors?

Second-generation antihistamines like loratadine (Claritin) or fexofenadine (Allegra) are safest for older adults. They cause less drowsiness and don’t interfere with brain function like diphenhydramine. But even these should be used with caution if the person has kidney problems, glaucoma, or an enlarged prostate. Always check with a doctor or pharmacist first.

How long is too long to use a nasal decongestant spray?

Three days. That’s it. Using nasal sprays like Afrin for longer than 72 hours causes rebound congestion-your nose becomes dependent on the spray to stay clear. You’ll end up needing more and more just to breathe. It’s a cycle that’s hard to break. If congestion lasts longer than a week, see a doctor instead.

Are natural remedies safer than OTC allergy meds?

Some are. Saline nasal rinses, air purifiers, and avoiding allergens are completely safe and often effective. Honey and herbal supplements? Evidence is weak. But they’re not dangerous like decongestants. Still, don’t assume “natural” means harmless. Some herbs interact with medications. Always tell your doctor what you’re taking-even if it’s tea or a supplement.

Final Thought: Just Because It’s OTC Doesn’t Mean It’s Safe

You wouldn’t take a prescription drug without reading the label. Why treat OTC meds any differently? They’re not candy. They’re powerful chemicals with real consequences. Whether you’re 22 or 72, whether you’re just fighting pollen or managing chronic asthma, your health is too important to guess with.

Read the ingredients. Know your conditions. Talk to a pharmacist. If your symptoms don’t improve in 10 days, see a doctor. There’s a better way to breathe-without risking your heart, your liver, or your life.