What cold medicine can I take before allergy testing? A guide to safe and unsafe options

With more than 50 million Americans experiencing allergies each year, many will undergo allergy testing. For those with cold symptoms, understanding what cold medicine can I take before allergy testing is crucial, as many common products can interfere with test accuracy.

Quick Summary

Allergy testing requires discontinuing certain cold medications, particularly those containing antihistamines, to ensure accurate results. Safe alternatives like plain decongestants or acetaminophen are acceptable, but combination products should be avoided.

Key Points

• Avoid All Antihistamines: The most critical rule is to stop taking any cold or allergy medication containing an antihistamine, as it will prevent your body from reacting during the test.

• Read All Labels Carefully: Combination cold and flu products, including those for nighttime relief, often contain hidden antihistamines that can interfere with test results.

• Stick to Safe Alternatives: Use plain decongestants (like Sudafed), plain pain relievers (like Tylenol), or plain expectorants (like Mucinex) if you need relief before your test.

• Know the Stopping Times: Oral antihistamines typically require a 5-7 day pause before testing, while some nasal and eye antihistamines may only need 1-3 days.

• Consult Your Physician: Never stop a prescription medication, including certain antidepressants or beta-blockers, without discussing it with your doctor first.

• Continue Asthma Medication: It is generally safe and important to continue taking your regular asthma medications, such as inhalers and Singulair, before your allergy test.

• Discuss All Medications: Provide your allergist with a complete list of all medications, supplements, and vitamins you are taking to ensure a safe and accurate test.

Accurate allergy testing is the cornerstone of an effective allergy management plan, helping pinpoint specific triggers so you can get the right treatment. However, a significant part of preparing for an allergy test involves adjusting your medication intake, especially if you are managing a cold. The key factor is avoiding antihistamines, as they block the allergic reaction your doctor is trying to observe during a skin prick or intradermal test. Knowing which over-the-counter (OTC) cold products contain these interfering ingredients is essential.

Why Cold Medications Can Interfere with Allergy Testing

Allergy skin tests are designed to provoke a small, controlled allergic reaction on your skin. When the test is performed, a tiny amount of a potential allergen is introduced. If you are allergic, your body's immune system releases histamine, causing a small, raised bump, or wheal, to form. Antihistamines, the primary ingredient in many cold and allergy medications, work by blocking this very histamine response. If you have an antihistamine in your system, it can prevent your body from reacting to the allergens during the test, leading to a false-negative result and potentially an incorrect diagnosis. This is why all oral antihistamines and most antihistamine nasal sprays and eye drops must be stopped for a specified period before testing.

Medications to AVOID Before Your Allergy Test

To ensure the accuracy of your test, it is vital to avoid all medications that contain antihistamines. The required stopping time can vary, so always confirm with your allergist's office, but general guidelines exist.

Oral Antihistamines and Combination Cold Medications

Most people know that allergy medications like Zyrtec, Claritin, and Allegra are antihistamines. However, it's easy to overlook that many common cold and flu remedies also contain them. For instance, any product labeled 'PM' or 'Nighttime' is almost certain to include a sedative antihistamine, like diphenhydramine.

Common medications to stop at least 5-7 days prior include:

• Second and Third-Generation Oral Antihistamines (stop 5-7 days prior):
  • Allegra (Fexofenadine)
  • Claritin, Alavert (Loratadine)
  • Zyrtec (Cetirizine)
  • Xyzal (Levocetirizine)
• First-Generation Oral Antihistamines and Sleep Aids (stop 5 days prior):
  • Benadryl (Diphenhydramine)
  • Unisom, Tylenol PM, Advil PM (contain Diphenhydramine)
  • Dramamine (Dimenhydrinate)
• Combination Cold/Flu Products (check labels, stop 5-7 days prior):
  • NyQuil
  • DayQuil (if containing an antihistamine)
  • Theraflu

Antihistamine Nasal Sprays and Eye Drops

Don't forget about topical antihistamines. While they act locally, they can still interfere with skin test results.

• Nasal Sprays (stop 1-3 days prior): Astelin, Astepro (Azelastine), Dymista (Azelastine and Fluticasone)
• Eye Drops (stop 1-3 days prior): Pataday, Patanol (Olopatadine), Zaditor, Alaway (Ketotifen)

Safe Cold and Pain Medications to TAKE Before Your Allergy Test

Relief is still possible, even without antihistamines. Several common cold and pain medications do not affect allergy skin test results and are generally safe to continue using.

Plain Decongestants

These medications help clear nasal congestion but do not block the histamine response. Look for products that contain only a decongestant and no other active ingredients.

• Sudafed (Pseudoephedrine): The plain formula is safe to take.
• Phenylephrine: Often found in some OTC decongestants.

Pain Relievers and Fever Reducers

Over-the-counter pain relievers that are not also antihistamines can be used to manage aches, pains, and fever.

• Tylenol (Acetaminophen): Plain acetaminophen is a safe option. Be careful to avoid "Tylenol PM".
• NSAIDs (Ibuprofen, Naproxen): While generally okay, some allergists recommend stopping these a few days prior to minimize bruising or bleeding from the skin test, so it is best to check with your provider.

Expectorants and Cough Suppressants

These address coughs and chest congestion without containing antihistamines.

• Mucinex (Guaifenesin): The plain expectorant formula is safe. Avoid "Mucinex Allergy" which contains fexofenadine.
• Delsym (Dextromethorphan): The plain cough suppressant is generally fine.

Comparison of Safe vs. Unsafe Cold Medications

This table provides a quick reference for common cold medication ingredients and their suitability before allergy skin testing.

Type of Medication	Safe for Testing?	Examples	Why it Matters
Oral Antihistamines	NO	Zyrtec, Claritin, Allegra, Benadryl	Blocks histamine, causing false-negative results.
Combination Cold Products	NO	NyQuil, DayQuil (with antihistamine)	Contain antihistamines and should be avoided.
Antihistamine Nasal Sprays	NO	Astelin, Astepro	Blocks local histamine response.
Plain Decongestants	YES	Plain Sudafed (Pseudoephedrine)	Relieves congestion without blocking histamine.
Plain Pain Relievers	YES	Plain Tylenol (Acetaminophen)	Does not interfere with histamine response.
Plain Expectorants	YES	Plain Mucinex (Guaifenesin)	Addresses congestion without affecting test.
Nasal Steroid Sprays	YES	Flonase (Fluticasone), Nasacort	Continue as directed; does not interfere.

Other Medications to Discuss with Your Doctor

It's important to have a comprehensive conversation with your allergist about all medications you are taking, as other drugs can also interfere with testing. These include:

• Certain Heartburn Medications: H2 blockers like Pepcid (famotidine) and Tagamet (cimetidine) have antihistamine properties and should be stopped 1-2 days prior. Proton pump inhibitors (PPIs) like Prilosec and Nexium are typically safe to continue.
• Antidepressants: Tricyclic antidepressants (e.g., doxepin, amitriptyline) and some atypical antidepressants can interfere with skin testing and should be discussed with your prescribing physician before stopping. SSRIs are usually safe.
• Beta-Blockers: These medications, used for blood pressure or heart conditions, can increase the risk of severe reactions during testing by interfering with the emergency treatment epinephrine. Do not stop these without a doctor's supervision.
• Asthma Medications: Asthma inhalers and controllers like Singulair are generally safe to continue. Stopping these could lead to uncontrolled asthma symptoms, making the test riskier.

Planning Ahead for Accurate Results

To ensure your allergy test provides the most accurate and useful information, the best course of action is to plan ahead. First, make a list of all your prescription and over-the-counter medications, including vitamins and supplements, to share with your allergist. Next, read all labels of cold and flu products carefully, even if they aren't primarily for allergies. Remember that many combination products hide antihistamines. Finally, always consult with your prescribing physician before stopping any necessary long-term medication.

Following these guidelines will help ensure that your allergy test provides clear, actionable results. The temporary inconvenience of stopping certain cold medicines is a small price to pay for an accurate diagnosis and a more effective long-term allergy treatment plan. For more detailed information on preparation, it's always best to consult directly with your allergist or a trusted source like the American College of Allergy, Asthma & Immunology(https://acaai.org/resource/allergy-testing/).

Frequently Asked Questions

Why can't I take antihistamines before an allergy test?

Allergy skin testing works by observing your body's natural histamine response to small amounts of allergens. Antihistamines block this histamine release, suppressing the reaction and leading to inaccurate, potentially false-negative, results.

What is considered a 'safe' cold medicine to take?

Safe cold medicines are those that do not contain antihistamines. This includes single-ingredient products like plain Sudafed (pseudoephedrine) for congestion, plain Tylenol (acetaminophen) for pain/fever, or plain Mucinex (guaifenesin) for chest congestion.

Can I take Tylenol PM or other 'PM' medications?

No, you should not take Tylenol PM or any other medication labeled 'PM' before an allergy test. The 'PM' indicates the presence of an antihistamine, usually diphenhydramine, which would interfere with your test results.

What if I accidentally took an antihistamine before my test?

If you accidentally take an antihistamine, you must inform your allergist immediately. The test will need to be rescheduled, as the results would be unreliable. Taking the test while on an antihistamine is a waste of time and resources for both you and your doctor.

Do I need to stop using my nasal steroid spray?

No, you do not need to stop using most steroid nasal sprays, such as Flonase (fluticasone), before your allergy test. They do not contain antihistamines and will not interfere with skin test results.

How long do I need to stop taking oral antihistamines before testing?

The standard recommendation is to stop taking oral antihistamines for 5 to 7 days prior to your allergy skin test. The exact timeframe can vary based on the specific medication and your doctor's protocol.

What about acid reflux medication like Pepcid or Zantac?

H2 blockers, such as Pepcid (famotidine) and Tagamet (cimetidine), have antihistamine effects and should be stopped 1-2 days before testing. Other acid reflux medications, like Proton Pump Inhibitors (PPIs), are generally safe to continue.