Allergy Meds Not Working? Causes and Relief


Why do antihistamines stop working?

Antihistamines can stop working because your allergies might be getting worse or you might have immune system changes due to aging. You also might not be taking the medication as directed. If you take an antihistamine after being exposed to an allergy trigger, it won’t work as well.

When you suffer from allergies, antihistamines are often the first defense against itchy, watery eyes and a runny nose. Yet sometimes, they stop working. Many medications cause drug resistance and tolerance, which cause the body to stop responding well to the medication. But that’s not quite the case with antihistamines. When these allergy medications stop working, it’s often more complicated to figure out why.

How Do Antihistamines Work?

When your body is exposed to an allergen, it causes your immune system to start an immune response. During this response, the body releases a chemical called histamine. Histamine’s role is to rid your body of the allergen by triggering inflammation, producing mucus, and irritating the eyes, nose, and skin.

Antihistamines work by stopping the body from releasing histamine. And with no (or reduced) histamine, most patients experience fewer allergy symptoms.

Why Do Antihistamines Stop Working?

In some patients, antihistamines stop working after months or even years of use. Sadly, the people who most experience the most reduced benefit often suffer from chronic and severe allergy symptoms.

There are various reasons antihistamines may stop working. Here are some of the most common:

New or Worsening Allergies

One reason antihistamines quit working may be because you have new allergies or your allergies have gotten worse. In people with multiple allergy triggers, the immune response may strengthen over time, making your allergy symptoms worsen. And the worse your allergies are, the less effective antihistamines become.

Climate Change

Another reason your allergy medication quit working may result from climate change. With warmer weather, growing seasons have lengthened, and the pollen season now lasts longer than before. Heavy pollution, drought, and other climate-related issues can exacerbate allergies.

Immune System Changes

As you age, your immune system changes. It may not function as well or be as strong as it once was and, therefore, it reacts in different ways. Sometimes, this change manifests in not responding to certain medications, including antihistamines.

Not Taking Medication as Directed

While you can take antihistamines anytime you have an allergic reaction, to be most effective, take the medication daily during peak allergy season. In many cases, antihistamines work better when you take them before the allergic reaction begins and continue throughout the duration of exposure. If you stop the medication because allergy symptoms go away, symptoms can be hard to get under control.


Long-term stress disrupts your immune system and worsens allergies by increasing sensitivity to allergens and strengthening your immune response. When your stress levels increase, antihistamines may have a weakened effect and provide less relief than in less stressed periods.

Non-Allergic Reaction

You may experience what appears to be allergy symptoms but is actually a non-allergic reaction. Because the immune system isn’t releasing histamines, antihistamines don’t work. Things that cause non-allergic reactions include:

  • Pollution
  • Cleaning supplies
  • Smoke
  • Perfumes and cologne
  • Artificial scents
  • Viruses

If you have allergy-like symptoms but don’t find relief from antihistamines, pay attention to other things in your environment that could be the culprit.

What to Do When Antihistamines Stop Working?

If antihistamines did work for you but stopped for some reason, there are things you can do to address your symptoms. For those who experience different allergy symptoms now than in the past, changing antihistamines may help. In other cases, adding a nasal rinse or spray may help with sinus-related symptoms that aren’t responding to antihistamines.

Reducing exposure to allergens can also help you manage your allergies. Avoiding peak pollen times, wearing a mask, and eliminating dust-harboring areas in your home like carpets, drapes, and upholstered furniture can also reduce your allergy symptoms.

When allergies impact how you function and don’t respond to antihistamines, consider immunotherapy. Immunotherapy offers long-lasting relief from allergy symptoms. It desensitizes the immune system to allergens so that it stops reacting when exposed. This results in long-term relief from your allergies.

Take Our Allergy Assessment

If antihistamines no longer offer you the allergy relief you want, allergy immunotherapy may. Take our two-minute assessment to see if you’re a candidate and start your journey to an allergy-free life today!

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