The safest antihistamines are generally second-generation, non-drowsy types like loratadine (Claritin), fexofenadine (Allegra), and cetirizine (Zyrtec), with loratadine often cited as having the best side-effect profile (less drowsiness) for long-term use, though fexofenadine is also very safe, while cetirizine is effective but more likely to cause drowsiness. Always check with a doctor or pharmacist to pick the best one for you, especially if pregnant, breastfeeding, or taking other medications, as first-generation antihistamines (like diphenhydramine) are more sedating and less recommended.
Antihistamines much less likely to cause drowsiness include:
The optimal way to avoid these problems is to use antihistamines with the highest level of cardiovascular safety, e.g. bilastine, which does not affect the CYP3A4 isoenzyme, nor the QT interval, even when overdosed.
Side effects of H2 (digestive) antihistamines are uncommon but can include: Fatigue. Diarrhea or constipation. Joint or muscle pain.
The choice between Claritin and Zyrtec depends on individual needs. Claritin has fewer side effects and is suitable for long-term use, while Zyrtec acts faster and is more effective at relieving severe symptoms. However, Zyrtec may cause drowsiness. Always consult a healthcare provider.
Kidney disease. Liver disease. An unusual or allergic reaction to cetirizine, other medications, foods, dyes, or preservatives. Pregnant or trying to get pregnant.
Common Claritin side effects include headache, dizziness, and digestive side effects such as nausea. Less commonly, some people may experience dry mouth, drowsiness, or fatigue. Claritin side effects are typically mild and can be managed at home.
Older adults should ideally use second-generation antihistamines (like cetirizine, loratadine, or fexofenadine) as they are less likely to cause drowsiness and cognitive impairment compared to first-generation antihistamines.
Excess histamine can cause a variety of different symptoms which very often mimic allergic reactions. The most common symptoms are rashes (e.g. hives), itching, flushing, irritable bowel syndrome (IBS), indigestion, breathlessness, palpitations, migraines, dizziness, anxiety/panic, joint aches and nasal congestion.
H1 first-generation antihistamines: Common adverse effects include sedation, cognitive impairment, and anticholinergic adverse effects such as dry mouth, urinary retention, constipation, and blurred vision. Dizziness, tinnitus, and delirium may occur at high doses.
Do antihistamines raise blood pressure? Oral antihistamines, such as Benadryl, Zyrtec, and Claritin, aren't known to increase blood pressure. Other antihistamine forms also aren't known to have a major effect on blood pressure.
People with conditions like glaucoma, enlarged prostate, heart disease, high blood pressure, asthma, liver or kidney disease, epilepsy, overactive thyroid, diabetes, or those who are pregnant/breastfeeding, or giving them to young children (under 2-6 years), should avoid or be cautious with antihistamines, especially older, sedating types, and should consult a doctor or pharmacist first due to risks like worsening urinary retention, glaucoma, or causing serious harm in kids.
During an allergic reaction, histamines bind to receptors along the blood vessels, making them expand and become more permeable so white blood cells can attack the pathogen. Antihistamines block this mechanism, in effect narrowing the blood vessels.
Fexofenadine (Allegra)
It's one of the least sedating second-generation antihistamines, making it a safe option for long-term use if you take it as your doctor prescribes. While fexofenadine is generally well-tolerated, a few possible side effects may occur, although they are rare.
non-drowsy antihistamines that are less likely to make you feel sleepy – such as acrivastine, cetirizine, fexofenadine and loratadine.
Natural Antihistamine Herbs: Tea and Plant Compounds That Support Histamine Balance
Medical Conditions
Autoimmune disorders affect immune system function, which might lead to more histamine being released (11). Another condition causing elevated histamine levels is mastocytosis, rare disorder involving abnormal mast cell growth—the cells that make and store histamine (12).
How is histamine intolerance diagnosed?
Coffee contains only a small amount of histamine, but it can still trigger symptoms in individuals with histamine intolerance or mast cell activation syndrome (MCAS). Factors such as the roast level, bean type, and brewing method all influence histamine levels. Dark roasts and cold brew are often better tolerated.
Be aware, too, that first-generation antihistamines typically are not recommended for adults 65 and older. That's because they have something called anticholinergic properties. Research suggests those properties might raise the risk of dementia.
Allergy Medications
First generation antihistamines, while very effective at controlling symptoms, are often associated with symptoms in older adults such as anxiety, confusion, sedation, blurred vision, reduced mental alertness, urinary retention and constipation.
Seniors: Seniors are more likely to experience side effects of this medication because of the pseudoephedrine. Discuss with your doctor or pharmacist the risks and benefits of this medication for you.
have ever had an allergy to loratadine or any other medicines. have severe liver failure. have an allergy to food additives. have epilepsy or another condition that puts you at risk of seizures or fits.
Studies employing self-report measures, such as diary cards, visual analogue scales, rating scales, and mood inventories have shown that the effect of loratadine on somnolence, fatigue, and mood was comparable to those found with placebo.
The basic version is mainly for classic allergy symptoms such as runny nose and sneezing – the only medicinal ingredient they contain is called an antihistamine. Examples of these are Allegra, Claritin, and Zyrtec. These will not affect your blood pressure at all.