Dec 11 (Reuters) - An oral immunotherapy drug for treating grass pollen allergies was backed by an independent advisory panel to the U.S. Food and Drug Administration on Wednesday.

The drug, Oralair, made by France's Stallergenes SA , is a tablet to be placed under the tongue and comprises extracts from five grass pollens mixed together - Kentucky bluegrass, Orchard, Perennial rye, Sweet vernal and Timothy.

The advisory panel voted 9-1 that available data supported the drug's efficacy in treating the allergy in patients five years of age or older.

While the panel voted unanimously in favor of the drug's safety in patients of 10 years to 65 years of age, it was divided about using the medicine in children, citing side effects.

Panelists also expressed concerns about the drug's use in asthmatic patients and in pregnant women and suggested conducting post-approval studies to test Oralair's effects on these populations.

While the FDA considers the recommendations of the advisory committee in deciding whether to approve a drug, it is not obligated to follow them.

Oralair was first granted marketing approval in 2008 in Germany and is currently marketed in 16 countries.

It is an immunotherapy that works by boosting the body's immune system and making it less sensitive to allergens.

Allergen-specific immunotherapies are ideal for patients whose symptoms are not adequately controlled by avoiding the allergens or by medicines, those suffering from allergy drug-related side effects, or who wish to reduce the long-term use of drugs.

The committee will discuss another immunotherapy for allergy, Grastek, made by Merck & Co on Thursday. Grastek is an experimental oral treatment for grass allergies and is sold as Grazax in Europe by Merck's partner ALK Abello .