Why Do Cancer Patients Take Claritin? Antihistamine Use

Explore why cancer patients take Claritin, an over-the-counter antihistamine, and its potential benefits in managing treatment side effects and allergic reactions.

Cancer patients often look to over-the-counter medicines like Claritin (loratadine) for help. These drugs aren’t just for sniffles. They can help fight treatment side effects and even have some anti-cancer powers.1

We are going to dive into why antihistamines, like Claritin, are used in cancer care. They’re not only for allergies. These medications can change the area around the tumor and make other cancer drugs work better. They’re becoming more important in fighting cancer.2

Key Takeaways

  • Cancer patients may take Claritin (loratadine) to manage treatment-related side effects and allergic reactions.
  • Antihistamines have been studied for their potential anticancer properties, including the ability to inhibit cancer cell proliferation and enhance the effectiveness of immunotherapy.
  • Retrospective studies have found that the concurrent use of antihistamines, particularly those targeting the histamine receptor H1 (HRH1), is associated with improved survival outcomes in cancer patients receiving immune checkpoint inhibitor therapy.
  • Ongoing research is exploring the combination of antihistamines and checkpoint inhibitors as a potential treatment approach to overcome resistance and improve immunotherapy outcomes.
  • The relationship between histamine, allergy, and cancer progression is complex, and modulating histamine signaling may impact tumor growth and the effectiveness of cancer treatments.

Introduction to Antihistamines and Cancer

Antihistamines were first made to help with allergies. Now, they might help with cancer too.1 People are looking into how to use these old drugs in new ways.1

Repurposing Old Drugs for Cancer Treatment

Scientists want to use old drugs like antihistamines in fighting cancer.1 This idea could make finding new cancer medicines faster.1 It also helps deal with the issues of using old drugs again.1

Claritin (Loratadine) and Other Antihistamines in Oncology

Claritin and some other antihistamines are being carefully studied for how they fight cancer.1 They might slow down cancer growth,1 help kill cancer cells,1 and make cancer treatments work better.3

Finding new uses for antihistamines could change cancer therapy for the better.1 As we learn more, these medicines could become key in treating cancer.1

Anticancer Properties of Antihistamines

Studies show antihistamines might help fight cancer. They stop cancer cells from multiplying, slow tumor growth, and cause some cells to die off.1 For example, astemizole slows down prostate cancer cell growth and causes cell death in cervical cancer cells.1

Inhibition of Cancer Cell Proliferation

Antihistamines can stop cancer cell growth.1 They work well together like thioridazine and loratadine to treat gut tumors. Even loratadine in tiny forms can stop pancreatic cancer from growing.1

Induction of Apoptosis and Autophagy

Antihistamines can make cancer cells die through apoptosis or autophagy.1 Some types, like desloratadine, look promising for treating bladder cancer.1

This means antihistamines might kill cancer cells directly, showing cancer-fighting potential. They might help balance cells and work against cancer in important ways.1

Antihistamines anticancer properties

Antihistamines and the Tumor Microenvironment

Antihistamines can change the tumor microenvironment. This is the area around a tumor. It’s made up of cells, signals, and a matrix that helps the tumor grow. Antihistamines may change how the immune system works near a tumor. This impacts T cells and macrophages near the tumor.245

Modulation of Immune Responses

Antihistamines target macrophages near the tumor. These macrophages can make a space where the immune system doesn’t work well. By changing these macrophages, antihistamines might help the body fight the tumor better.5

Targeting Tumor-Associated Macrophages (TAMs)

Histamine H1-receptor (H1R) signals can make macrophages act in a way that’s not good for fighting the tumor. This also stops CD8+ T cells from working right.5 Antihistamines that block the H1 receptor might help patients with melanoma or lung cancer do better with certain treatments.45 By blocking histamine, antihistamines could make T cells fight the tumor more and stop it from growing.4

Antihistamines may have a big impact on how a tumor gets its food and grows. Because of this, many people are excited about using them with other cancer treatments.245

Antihistamines and Immune Checkpoint Inhibitors

Scientists are looking into how antihistamines might help with cancer treatments. They are studying if using them with immune checkpoint inhibitor therapies can be effective. These inhibitors help our body fight cancer by freeing up special cells called T cells. Sometimes, though, the treatment might not work for everyone. It seems that using antihistamines with these treatments could help more people. This could make the treatment better.26

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For people with melanoma or lung cancer, taking antihistamines with the main treatment might be a good idea. It has shown to help them do better. This was also true for those with breast or colon cancer, but they need to study more people to be sure. It looks like having a lot of a certain receptor in the tumors could mean the main treatment won’t work as well, and patients might not do as well.2

In studies on animals with breast cancer and melanoma, using antihistamines with the main treatment made it work better and made the animals live longer. People with cancer who had a lot of histamine in their blood showed not as good results with the main treatment. This might mean high histamine levels can make the treatment less effective.2

Pantziarka, P. et al. in BMJ, 2018, said some old drugs, like Claritin, might be useful for cancer now. This thinking is getting popular. What Fritz I. et al. found in Allergy, 2020 was that using specific antihistamines helped people with melanoma live longer. This shows the potential of antihistamines to help cancer patients.1

H1-antihistamines might make the main cancer treatment work better. For those with melanoma or lung cancer, taking these antihistamines during treatment showed better results. Also, using them with the main treatment could be particularly helpful for people with high histamine levels. It might make their treatment work even better.6

Clinical Evidence of Antihistamine Use in Cancer

Some studies looked at cancer patient records. They found using antihistamines helped patients live longer. These medicines seem to make cancer treatments work better.1

Retrospective Studies on Antihistamine Use and Survival

In one study, two antihistamines helped people with breast cancer live longer.1 Others found the same for melanoma patients using these two medicines.1

Researchers also checked if allergies change cancer risk. Some found having allergies might protect against certain cancers, like melanoma.1

Ongoing and Planned Clinical Trials

Now, scientists are planning new tests. They want to see how antihistamines can help even more cancer patients.1 These tests could give us clear answers on these medicines’ benefits and safety.1

In a study of over 4,500 lung cancer patients, 28.7% used loratadine.7 The ones who used loratadine lived longer.7 Taking more loratadine meant less chance of dying from lung cancer.7

Those who used loratadine did better than those who didn’t. They lived longer without the disease.7 Taking loratadine was also linked to lower risk of dying when combined with other drugs.7

Scientists found other drugs that help lung cancer patient survival.7 There were big differences in how many patients took these medicines, depending if they lived or not.7

Loratadine seems to act against cancer by changing how some cells die. This might be why cancer patients live longer when they take it.7

why do cancer patients take claritin

Claritin (Loratadine) as a Potential Adjuvant Therapy

Claritin (loratadine) is considered a helper treatment for cancer alongside the regular ones. It’s studied for changing the tumor’s environment to help immunotherapy work better.1

Managing Treatment Side Effects and Allergic Reactions

Cancer patients use Claritin for two main reasons. First, to ease side effects like skin issues or allergies from treatment. And second, it might make immunotherapy more effective.8 Researchers are looking into the combined use of Claritin and other antihistamines in fighting cancer.3

One common problem with cancer medicine is bone pain, especially with Neulasta. Claritin is given to ease this Neulasta-related pain.8 While it’s not clear how well Claritin works for this, some studies show it could help a bit.8

Antihistamines that aim for the HRH1 receptor can help cancer patients taking immunotherapy live longer.3 Newer H1-antihistamines like Claritin are connected to better results with immunotherapy.3

The study of using Claritin and other antihistamines with cancer treatment is active. It aims to lessen side effects and boost immunotherapy success.183

Histamine and Allergy in Cancer Progression

Histamine is part of allergic reactions and cancer growth.5 It’s often found at high levels in cancer and allergic people.5 This includes breast and colon cancer.5

In many cancers, high histamine is linked to T-cell problems.5 This can make tumors grow faster. It also stops the body from fighting cancer with immunotherapy. This was seen in mice with allergies.5

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High histamine, from allergies or cancer cells, changes the tumor’s space.52 The link between histamine, cancer, and allergies is not fully understood. But, scientists are looking into how changing histamine could help treat cancer better.52

Mechanisms of Action of Antihistamines

Antihistamines work in a few ways, such as blocking histamine receptors. This stops histamine from causing trouble. They also help with inflammation and immune responses.1

Histamine Receptor Antagonism

They stop histamine from working by blocking its receptors. This affects cells and the immune system, especially in tumors.1

Anti-Inflammatory and Immunomodulatory Effects

Antihistamines can help in reducing inflammation and changing the immune system. This could be good in fighting cancer.1

For example, loratadine might help prevent pancreatic cancer when used in tiny forms.1 Astemizole can slow down cervical cancer growth. Combining astemizole and gefitinib might help treat lung cancer.1

Desloratadine is seen as helpful in treating bladder cancer.1 Also, astemizole can boost the effect of certain drugs in breast cancer.1

Terfenadine, another type, might cause cell death in skin cancer cells.1 New treatments for leukemia have been found using cell patterns. Also, certain immune cells can help in colorectal cancer treatments.1

Desloratadine and loratadine could mean better chances for those with breast cancer.1 They also seem to help those with skin cancer live longer.1

Safety and Drug Interactions

Antihistamines are often safe, but we need to watch out for interactions with cancer treatments.9 Claritin interacts with 105 drugs. It’s mostly used for allergies and hives.10 There are 490 drugs that can interact with paclitaxel, a cancer treatment drug.

Potential Side Effects of Antihistamines

Antihistamines might cause a few side effects like feeling sleepy or having a dry mouth. These effects should be checked in someone with cancer.1 They might help stop cancer cells from growing or cause them to die. This shows they might help fight cancer.

Interactions with Cancer Treatments

Some antihistamines might not work well with certain cancer treatments. It’s important to think about this if we want to use antihistamines to help treat cancer.9 Warnings about using capecitabine and Claritin together weren’t found. But, experts use a system to show if combinations can be a problem. This system has categories like Major, Moderate, Minor, and Unknown. It helps figure out if interactions could be bad.1 Mixing antihistamines with some cancer drugs has done well in some cancer studies.

It’s very important to watch carefully for side effects and how drugs might interact. This is key when adding antihistamines in a cancer treatment plan.9 There’s a way to get drug warnings specific to you. A My Med List account can send you these alerts.

Patient Education and Counseling

More and more, antihistamines are being used in cancer care. It’s key to fully inform and counsel cancer patients. They should know how antihistamines can help them. This includes dealing with treatment-related side effects and making immunotherapy work better.2 There are important safety issues and side effects to talk about too.11 Talking openly and guiding patients is crucial. It helps them use antihistamines well in their cancer care plan.

For patient education and counseling to really work, healthcare pros must cover some key points with cancer patients:

  1. How antihistamines can help, like easing treatment-related side effects and making immunotherapy more effective.2
  2. Important safety points and side effects of antihistamines with the patient’s cancer treatments.11
  3. It’s vital to stick close to the treatment plan and tell the healthcare team about any issues.
  4. Open communication and teamwork between patient and pro are needed for antihistamine use in their cancer care plan.

By giving the right patient education and counseling, healthcare pros can help cancer patients a lot. They can make smart choices and use antihistamines well in their symptom management and cancer treatment plan.

Brand NamesUsesSide EffectsMissed DoseStorageOverdose
Alavert, Allergy Relief, Claritin, Loradamed, Triaminic Allerchews, among others11The drug is primarily used to ease allergy signs and treat hives11Common side effects include headaches and feeling sleepy11If a dose is missed, it can be taken as soon as remembered, unless close to the next scheduled dose11The drug should be stored at room temperature, in a dry place, away from children and pets11If an overdose is suspected, contact poison control or seek medical care immediately11
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Future Directions and Research Needs

The use of antihistamines in cancer treatment shows promise. They might work well with immune checkpoint inhibitors. But, we need more research to fully understand how they could help. Clinical trials should look at how safe and helpful these drugs are when combined with immunotherapy or other treatments. It’s also important to see if antihistamines can help in many types of cancer and for different people.

Looking back, studies found that antihistamines, which block HRH1, improved survival in lung cancer and melanoma patients.2 For patients with breast or colon cancer, the results were promising but not clear because the studies were small.2 We need more studies to see if antihistamines could really make a difference in treating cancer.

Some early research suggests that antihistamines could help by making the immune system attack cancer more effectively.2 They might work even better when used with checkpoint blockers in breast cancer and melanoma.2 These studies show that antihistamines may change the tumor environment, making immunotherapy work better.

In the future, we need well-planned trials to see if antihistamines should be used with immune checkpoint blockers and other cancer drugs. It’s also crucial to learn more about how antihistamines could help in various kinds of cancer and for different people. By studying the benefits of these drugs more, we could find new and better ways to treat cancer.


Using antihistamines like Claritin in cancer care is becoming more common. They can make immunotherapy work better and help with side effects.7 Studies show they might help change the tumor environment and boost the immune system. This could make patient outcomes better.7,12 Adding antihistamines into cancer treatments is looking hopeful for the future of personalized care.

Many studies and clinical trials point to the good of using antihistamines, like Claritin, in cancer care.8,7 They help not only with side effects but also with making immunotherapy work better. This might help beat resistance and make patients better.7,12

Researchers are still studying the use of antihistamines in cancer care.12 We need more clinical trials to check if they are safe and work well with other cancer treatments.7 Using antihistamines in overall cancer care shows promise for making patients better and pushing the field forward.


Why do cancer patients take Claritin?

Cancer patients use Claritin for two big reasons. It can help with skin and allergic reactions from treatment. Also, it might make immunotherapy work better by changing how the immune system and the tumor interact.

What are the potential benefits of antihistamines in cancer treatment?

New info shows that antihistamines like Claritin could slow the growth of cancer cells and cause them to die. They can also make the area around the tumor and the immune system better. People are also looking at them to see if they can improve certain immune therapies for cancer.

How do antihistamines interact with cancer treatments?

Antihistamines are usually safe, but they might interact with cancer treatments. It’s key to watch patients closely and manage any bad effects or how these drugs interact with others in the treatment plan.

What is the role of patient education in the use of antihistamines for cancer?

Teaching patients about antihistamines is now very important in cancer care. They need to know the good effects, how safe they are, and if they might interact with their other cancer drugs.

What are the future research directions for the use of antihistamines in cancer?

The next big steps in research include more clinical trials. These will look closely at using antihistamines with immunotherapy and other cancer treatments. Also, we should look at how antihistamines can help in different cancer types and in more patient groups.

Source Links

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7868613/
  2. https://www.mdanderson.org/newsroom/antihistamines-may-improve-immunotherapy-responses-study-finds.h00-159465579.html
  3. https://www.curetoday.com/view/some-allergy-medications-may-positively-influence-immunotherapy-responses-in-cancer-but-is-only-a-tip-of-the-iceberg-
  4. https://www.the-scientist.com/over-the-counter-antihistamines-could-help-against-cancer-69464
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10640902/
  6. https://www.healio.com/news/hematology-oncology/20220208/antihistamines-may-impact-response-to-immune-checkpoint-inhibitors-for-cancer
  7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10759632/
  8. https://www.drugs.com/medical-answers/you-claritin-neulasta-3548526/
  9. https://www.drugs.com/drug-interactions/capecitabine-with-claritin-490-0-1486-898.html
  10. https://www.drugs.com/drug-interactions/claritin-with-paclitaxel-1486-898-1778-0.html
  11. https://www.mskcc.org/cancer-care/patient-education/medications/adult/loratadine
  12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2829588/