Allegra Side Effects

by on June 11, 2012


Allegra side effect are very rare. In fact, the medication is now available over the counter in its prescription formula. In rare cases, individuals may have a serious allergic reaction to fexofenadine or other ingredients, but the most commonly experienced side effects of Allegra are headaches, diarrhea, stomach & back pain, high blood pressure, insomnia.

Common Allegra Side Effects

Only a small percentage of individuals will experience side effects when they take Allegra. These symptoms will usually improve with continued usage, but if they are severe or do not go away, contact your doctor.

  • Dizziness
  • Headache
  • Drowsiness
  • Vomiting
  • Diarrhea
  • Arm, leg, or back pain
  • Generalized aches and pain
  • Abnormal menstrual pain
  • Persistent cough
  • Nervousness
  • Nightmares

Common Allegra D side effects may also include:

  • Difficulty concentrating
  • Excitability, especially in children
  • Difficulty remembering
  • Dry mouth
  • Ringing in the ears
  • Difficulty sleeping (insomnia)
  • Stomach pain
  • Constipation


Most individuals who take Allegra or Allegra D do not experience drowsiness. Unlike its predecessor, terdenadine, fexofenadine is less likely to pass into the brain so there is a decreased chance of sleepiness. However, drowsiness can occur so it is very important that you know how Allegra will affect you before you drive, operate machinery, or perform other tasks that require you to be alert and focused.

Serious Allegra Side Effects

An allergic reaction is the most serious side effect reported by Allegra users. Do not take this medication if you are allergic to fexofenadine and contact your doctor immediately if you experience any of the symptoms below:

  • Hives
  • Severe itching
  • Breathing difficulties
  • Trouble swallowing
  • Skin rash
  • Swelling, especially of the face, throat, or tongue
  • Hoarseness

Because Allegra D also contains the stimulant pseudoephedrine, there are additional risks that could be serious. Contact your doctor immediately if you experience any of the symptoms below while taking Allegra D:

  • Fast or irregular heartbeat
  • Confusion
  • Severe dizziness
  • Unusual thoughts or behaviors
  • Unexplained weakness
  • Elevated or high blood pressure
  • Chest pain
  • Seizures
  • Anxiety
  • Hallucinations
  • Fever

Use In Children

Allegra has been approved as a safe and effective way to treat allergy symptoms in children as young as 2 years old. In the treatment of urticaria, Allegra may be administered to infants who are at least 6 months of age. Allegra oral suspension is recommended for children under 12, while Allegra tablets can be taken by patients 12 and over. Children under the age of four may experience serious or potentially fatal Allegra D side effects. Products containing pseudoephedrine and similar stimulants should not be given to children under four.


Classified as a pregnancy category C drug, Allegra and Allegra D are not recommended during pregnancy. It is not known what harm the medication may do to an unborn baby. If you are pregnant or plan to become pregnant, ask your doctor about safe allergy treatments that may work for you. Both fexofenadine and pseudoephedrine can pass through breast milk to a nursing infant. Do not take Allegra or Allegra D while breastfeeding unless instructed to do so by your doctor.

Allegra and Existing Conditions

Allegra (Fexofenadine) may cause serious complications to individuals with kidney disease. Pseudoephedrine can cause adverse reactions in patients with other conditions as well. Before taking Allegra or Allegra D, tell your doctor if you have ever been diagnosed with any of the following conditions. You may need to adjust your dosage of the medication or choose an alternative treatment.

  • Kidney disease
  • Urination difficulties
  • High blood pressure
  • Heart disease
  • Glaucoma
  • Thyroid disorders
  • Diabetes
  • An enlarged prostate

Other Medications

Allegra works safely with most other medications and supplements. There are a few substances that can decrease the effectiveness of Allegra or may increase the risk of side effects. Tell your doctor if you are taking any of the medications below before using Allegra:

  • The antibiotic erythromycin
  • Ketoconazole, an antifungal medication
  • St. John’s wort, although this product is unlikely to interfere with Allegra
  • Other medications to treat a cold or symptoms of allergies

Fruit juices, especially grapefruit juice, may decrease the body’s absorption of the drug and lower its concentration in the blood. Antacids with magnesium or aluminum, such as Mylanta, Maalox, etc. may have a similar effect and should be taken at least 2 hours before taking Allegra. Avoid the use of stimulants like caffeine, diet pills, Ritalin, etc. while taking Allegra D unless advised by a doctor.

Allegra and Allegra D are used by millions of individuals who seek relief from the symptoms of seasonal allergies. For most people, fexofenadine is a safe and effective treatment option. There are very few Allegra side effects and most people will not experience any abnormal symptoms while taking the medication, making it a reliable choice for adults and children.