Allegra’s active ingredient is fexofenadine hydrochloride, a second-generation antihistamine. The standard 24-hour tablet contains 180 mg of fexofenadine, while the 12-hour version contains 60 mg per tablet (taken twice daily). Beyond the active ingredient, the tablets contain about ten inactive ingredients that hold the pill together, coat it, and give it its distinctive peach color.
How Fexofenadine Works
Fexofenadine blocks histamine from attaching to H1 receptors throughout your body. Histamine is the chemical your immune system releases during an allergic reaction, and it’s responsible for the sneezing, itching, runny nose, and watery eyes that come with seasonal allergies. By occupying those receptors first, fexofenadine prevents histamine from triggering those symptoms.
What sets fexofenadine apart from older antihistamines like diphenhydramine (Benadryl) is that it barely crosses into the brain. First-generation antihistamines flood the central nervous system, which is why they cause drowsiness. Fexofenadine doesn’t occupy receptors in the brain in any meaningful way, so it relieves allergy symptoms without making you sleepy. This is also why it’s commonly recommended for older adults, who are more vulnerable to the sedating and cognitive effects of first-generation options.
Inactive Ingredients in the 180 mg Tablet
The inactive ingredients in a standard Allegra 24-hour tablet, as listed by the National Library of Medicine, are:
- Microcrystalline cellulose: a plant-based fiber that forms the bulk of the tablet
- Pregelatinized starch (corn): helps the tablet break apart in your stomach
- Croscarmellose sodium: another disintegrant that speeds up how quickly the tablet dissolves
- Magnesium stearate: a lubricant that prevents the powder from sticking to manufacturing equipment
- Colloidal silicon dioxide: keeps the powder flowing smoothly during production
- Povidone: a binder that holds the compressed ingredients together
- Hypromellose: forms the thin film coating on the outside of the tablet
- Polyethylene glycol: makes the film coating smooth and easier to swallow
- Titanium dioxide: a white pigment used in the coating
- Iron oxide blends: responsible for the tablet’s peach/brown color
Notably, the current tablet formulation does not list lactose as an inactive ingredient. However, older Allegra capsules (the 60 mg version) did contain lactose along with a gelatin shell, so if you’re looking at capsule-form Allegra, check the label. None of the standard Allegra tablets contain FD&C artificial dyes. The coloring comes entirely from iron oxides and titanium dioxide.
What’s in Allegra-D
Allegra-D is a different product that combines two active ingredients. The 24-hour version contains 180 mg of fexofenadine for allergy relief plus 240 mg of pseudoephedrine hydrochloride for nasal congestion. The fexofenadine portion releases immediately, while the pseudoephedrine is formulated for extended release throughout the day. Because pseudoephedrine is a decongestant that can raise blood pressure and heart rate, Allegra-D is kept behind the pharmacy counter in most states, even though it doesn’t require a prescription.
What’s in Children’s Allegra
The liquid suspension made for children contains 30 mg of fexofenadine per 5 mL (one teaspoon). The inactive ingredient list is quite different from the tablet. It includes sucrose and xylitol as sweeteners, flavoring agents, purified water, and xanthan gum as a thickener. It also contains potassium sorbate as a preservative and propylene glycol as a solvent. The liquid form uses sodium phosphate buffers to keep the pH stable, and it still contains titanium dioxide for its opaque white appearance.
Allegra Hives vs. Allegra Allergy
If you’ve noticed both “Allegra Allergy” and “Allegra Hives” on store shelves and wondered whether they’re different formulas, they’re not. Both contain 180 mg of fexofenadine hydrochloride with the same inactive ingredients. The packaging difference reflects the two FDA-approved uses of fexofenadine: seasonal allergy symptoms and chronic hives (urticaria). You’re getting the same tablet either way.
Why Grapefruit Juice Matters
One unusual thing about fexofenadine is that grapefruit juice, orange juice, and apple juice can reduce how much of the drug your body absorbs. Most drug-juice interactions involve the juice increasing drug levels, but fexofenadine works in reverse. These juices block a transporter protein in your intestinal wall that fexofenadine relies on to get absorbed. Drinking grapefruit juice with Allegra reduces absorption by roughly 25%, which could make the medication noticeably less effective. The simplest fix is to take Allegra with water rather than fruit juice.