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Generic Name: timothy grass pollen allergen extract (TIM oh thee grass PAW len AL er gen EX tract)
Brand Name: Grastek
Physician reviewed Grastek patient information - includes Grastek description, dosage and directions.
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Drug Information:
Grastek is made from certain pollens that can cause seasonal allergies (hay fever). Grastek is used to help your body develop an immunity to certain pollens that can cause allergy symptoms such as sneezing, itching, and watery eyes. Grastek is for use in adults up to age 65, and children who are at least 5 years old. This medicine will not provide immediate relief from allergy symptoms. Grastek may also be used for purposes not listed in this medication guide. You should not use this medicine if you have uncontrolled asthma, or if you have a history of allergic reaction to a pollen-extract medicine, or allergic reaction that affected your esophagus. Learn more

Grastek Side Effects

Grastek Side Effects

Note: This document contains side effect information about timothy grass pollen allergen extract. Some of the dosage forms listed on this page may not apply to the brand name Grastek.

In Summary

Common side effects of Grastek include: mouth edema, throat irritation, and pruritus of ear. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to timothy grass pollen allergen extract: sublingual tablet


Sublingual route (Tablet)

Timothy Grass Pollen Allergen Extract can cause life-threatening allergic reactions such as anaphylaxis and severe laryngopharyngeal restriction. Do not administer Timothy Grass Pollen Allergen Extract to patients with severe, unstable or uncontrolled asthma, and observe patients in the office for at least 30 minutes following the initial dose. Prescribe auto-injectable epinephrine, instruct and train patients on its appropriate use, and instruct patients to seek immediate medical care upon its use. Timothy Grass Pollen Allergen Extract may not be suitable for patients with certain underlying medical conditions that may reduce their ability to survive a serious allergic reaction, or in patients who may be unresponsive to epinephrine or inhaled bronchodilators (eg, those taking beta-blockers).

Along with its needed effects, timothy grass pollen allergen extract (the active ingredient contained in Grastek) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking timothy grass pollen allergen extract:

More common

  • Itching of the ears, mouth, or tongue
  • numbness or tingling feeling around the mouth
  • sore throat
  • swelling of the mouth

Less common

  • Chest discomfort
  • difficult or labored breathing
  • difficulty swallowing
  • hives or welts, itching, or skin rash
  • redness, swelling, or soreness of the tongue or in the mouth
  • runny nose
  • swelling of the lips
  • tightness in the chest

Incidence not known

  • Cough
  • dizziness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fast heartbeat
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • sweating
  • unusual tiredness or weakness

Some side effects of timothy grass pollen allergen extract may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

  • Acid or sour stomach
  • dry throat
  • headache
  • heartburn
  • nausea

Incidence not known

  • Diarrhea
  • drowsiness

For Healthcare Professionals

Applies to timothy grass pollen allergen extract: sublingual tablet


The most common side effects were ear pruritus, oral pruritus, tongue pruritus, mouth edema, and throat irritation.


Uncommon (0.1% to 1%): Systemic allergic reactions (including anaphylaxis)

Postmarketing reports: Anaphylactic reaction, angioedema


Very common (10% or more): Throat irritation (up to 22.6%)

Common (1% to 10%): Pharyngeal edema, dry throat, oropharyngeal pain, nasal discomfort, throat tightness, dyspnea, pharyngeal erythema, cough, nasal congestion, sneezing

Uncommon (0.1% to 1%): Rhinorrhea, dysphonia

Postmarketing reports: Asthma exacerbation, hoarseness, laryngitis, induced asthma exercise, decreased forced expiratory volume, hyperventilation, laryngeal discomfort, decreased oxygen saturation, decreased peak expiratory flow rate, pneumonia, respiratory distress, status asthmaticus, decreased vital capacity, wheezing


Common (1% to 10%): Chest discomfort

Postmarketing reports: Chest pressure, increased heart rate, irregular heart rate, hypotension


Common (1% to 10%): Pruritus, urticaria

Postmarketing reports: Facial erythema, rash


Very common (10% or more): Oral pruritus ( up to 26.7%), Lip pruritus (up to 11.1%), mouth edema ( up to 11.1%)

Common (1% to 10%): Lip pruritus, oral paresthesia, tongue pruritus, lip swelling, swollen tongue, dyspepsia, oral hypoesthesia, nausea, oral discomfort, oral mucosal erythema, lip edema, glossitis, stomatitis, tongue disorder, tongue edema, glossodynia, dysphagia, palatal edema, glossodynia

Uncommon (0.1% to 1%): Abdominal pain, gastroesophageal reflux, mouth swelling, oral/pharyngeal itching

Postmarketing reports: Oral ulceration, ulcerative colitis exacerbation, diarrhea, eosinophilic esophagitis, oral pain, throat pruritus, vomiting

Nervous system

Common (1% to 10%): Headache

Postmarketing reports: Altered state of consciousness, difficulty speaking, dizziness, drowsiness, tremor


Very common (10% or more): Ear pruritus (up to 12.5%)

Common (1% to 10%): Fatigue

Uncommon (0.1% to 1%): Ear itching

Postmarketing reports: facial edema, sensation of foreign body, neck swelling

Editorial References and Review

Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.

Source: Drugs.com Grastek