You may have heard that Benadryl — one of the many brand names for diphenhydramine — isn’t safe for people with asthma. “I’ve been told to avoid Benadryl,” shared a MyAsthmaTeam member. But does that advice hold true for everyone with asthma?

Diphenhydramine is an antihistamine medication that can be used to treat symptoms of a cold or allergies. If you have asthma, you might wonder if taking this medication will help or hurt you. Continue reading to learn more about diphenhydramine and whether it’s safe for people with asthma.

What Is Diphenhydramine?

Diphenhydramine is a first-generation antihistamine, which means it was the first type approved by the U.S. Food and Drug Administration (FDA). You can buy it over the counter (OTC) to temporarily relieve allergy or cold symptoms including:

• Runny nose
• Sneezing
• Itchy or watery eyes
• Itchy throat or nose

Diphenhydramine has other uses too, such as helping you fall asleep. When applied to skin, diphenhydramine can help relieve pain and itching caused by a bug bite, rash, or other skin issues.

Diphenhydramine is found in a number of OTC products, including combination cough, cold, and allergy medications. Combination products that may contain diphenhydramine include:

• Tylenol PM
• Robitussin Night Time Cough and Cold
• Sudafed PE Severe Cold
• Theraflu Nighttime Severe Cold and Cough
• Unisom with Pain Relief

This is not a complete list — check medication labels to ensure you don’t take more than one drug that has diphenhydramine.

How Is Diphenhydramine Usually Taken?

Most people take diphenhydramine only when needed. It’s available in tablet, capsule, or liquid form. Always take diphenhydramine exactly as your doctor advises or according to the instructions on the package. Some people may have to take diphenhydramine several times throughout the day because it is a short-acting drug — it works quickly, but the effects wear off soon.

How Does Diphenhydramine Work?

Diphenhydramine blocks the effect of histamine, a chemical released by your immune system in response to something harmful. Histamine sets off an inflammatory response that helps your immune system fight foreign invaders, like bacteria and viruses.

Although this response is helpful for fending off illness-causing threats, it can sometimes have unwanted effects. If you have allergies, your immune system can overreact to a harmless substance — such as pollen, dust, or pet dander — triggering the release of histamine and the resulting allergy symptoms.

What Are the Side Effects of Diphenhydramine?

Diphenhydramine is also known as a sedating antihistamine, so it’s no surprise that one of its most common side effects is drowsiness. Several MyAsthmaTeam members have experienced this side effect, with one sharing, “Benadryl makes me goofy.”

Other side effects of diphenhydramine include:

• Dizziness
• Headache
• Thickened mucus
• Dry mouth
• Dry eyes
• Difficulty urinating
• Constipation
• Low blood pressure

Why Might People With Asthma Take Diphenhydramine?

People with asthma may take diphenhydramine to treat the symptoms of a cold or allergies. In some people, allergens (normally harmless substances) trigger asthma symptoms. This type of asthma is known as allergic asthma. In these individuals, asthma symptoms worsen following exposure to common allergens, such as:

• Pollen
• Pet dander
• Dust mites
• Mold

Allergens like these can prompt the release of higher levels of histamine, causing your airways to narrow and increasing mucus production. An antihistamine like diphenhydramine can help block the effects of histamine and improve allergy symptoms.

Although diphenhydramine may temporarily improve the symptoms of asthma related to allergies, it can’t stop an asthma attack or improve core asthma symptoms, such as:

• Shortness of breath
• Cough
• Wheezing
• Chest tightness

Is Diphenhydramine Safe for People With Asthma?

Before 1992, diphenhydramine was contraindicated (not recommended) for people with asthma. Experts believed that diphenhydramine and other first-generation antihistamines would dry out mucous membranes too much and cause harm.

In 1992, the FDA removed asthma from the list of contraindications to diphenhydramine. Experts believe that the drug’s drying effect isn’t strong enough to harm people with asthma.

Although diphenhydramine is no longer contraindicated for people with asthma, this doesn’t mean that experts recommend its use. Diphenhydramine can cause side effects and has drug interactions that can make it unsafe for some people to take. You should seek medical advice from your doctor before taking diphenhydramine if you have asthma.

Who Should Avoid Diphenhydramine?

Talk to your doctor about adding diphenhydramine to your treatment plan. Some people shouldn’t take diphenhydramine, including:

• Children under 6 years old (unless instructed by their doctor)
• Adults age 65 or older
• People who are pregnant or breastfeeding
• People with certain medical conditions, such as heart problems (including high blood pressure), kidney issues, or thyroid disease
• People with increased intraocular pressure (high pressure in the eye)

Because drowsiness is a common side effect of diphenhydramine, you should avoid taking it if you need to be awake and alert, such as when driving or working with heavy machinery. Taking diphenhydramine during the day may make it harder to concentrate. Drowsiness and dizziness caused by diphenhydramine can also increase the risk of falling, especially in older adults.

Diphenhydramine can also interact with other drugs that cause drowsiness, such as opioid pain relievers, alcohol, and sleep medications. Taking diphenhydramine with other medications that can make you feel sleepy may result in more severe side effects and increase your risk of falling.

Diphenhydramine may also interact with some antidepressants. It’s important to check with your doctor or pharmacist about possible drug interactions before taking diphenhydramine.

Other Treatments for Allergies

Diphenhydramine is just one of several types of antihistamines. Newer, second-generation antihistamines are generally considered safer because they cause fewer side effects and drug interactions. Also, these long-acting medications usually need to be taken just once a day. Second-generation antihistamines that are available without a prescription include:

• Cetirizine (such as Zyrtec)
• Loratadine (such as Claritin)
• Fexofenadine (Allegra)
• Desloratadine (Clarinex)

One MyAsthmaTeam member shared, “I take cetirizine by day so I can minimize Benadryl by day, which can affect driving, work, and daily tasks.”

You should also talk to your doctor about other treatments for allergies, such as:

• Nasal sprays like fluticasone (such as Flonase) and azelastine (Astelin, Astepro)
• Decongestants like pseudoephedrine (such as Sudafed) and phenylephrine (such as Sudafed PE)
• Inhaled corticosteroids like fluticasone propionate (Flovent) and budesonide (Pulmicort Flexhaler)
• Inhaled bronchodilators like an albuterol sulfate inhaler (Proair, Proventil, or Ventolin HFA)
• Leukotriene modifiers like montelukast (Singulair) and zafirlukast (Accolate)
• Immunotherapy, including allergy shots or allergy drops

Speak With Your Doctor Before Taking Benadryl

If you have a cold, allergies, or allergic asthma, talk with your doctor before taking an antihistamine like diphenhydramine — or any other OTC medication. During the discussion, ask questions such as:

• Will diphenhydramine cause problems with any of my other medical conditions, including asthma?
• Does diphenhydramine interact with any medications I’m taking?
• How much and how often should I take diphenhydramine?
• How long should I take diphenhydramine?
• Can I give diphenhydramine to my child?
• Are there activities I should avoid when taking diphenhydramine?

Even though it’s sold over the counter, Benadryl can come with several risks, particularly for people who have another condition, such as asthma. Safety is essential, and having these conversations with your doctor can help you avoid issues down the road.

Talk With Others Who Understand

MyAsthmaTeam is the social network for people with asthma and their loved ones. On MyAsthmaTeam, more than 10,000 members come together to ask questions, give advice, and share their stories with others who understand life with asthma.

Have you taken diphenhydramine to treat cold or allergy symptoms? Did you have any side effects? Share your experience in the comments below, or start a conversation by posting on your Activities page.