SPOKANE, Wash. — A company that makes allergy products is planning a major expansion in Post Falls, Idaho, announcing last week it will build the world's largest allergen raw material production plant.

ALK-Abello A/S of Denmark will break ground Wednesday on the $50 million plant in a business park in Post Falls, about 15 miles east of Spokane.

The company also looked at two sites on the Washington side of the border, but Idaho provided a better business environment, said Miles Guralnick, president of Biopol Laboratory Inc. and Vespa Laboratories, which are partners in the project.

"The state of Idaho is very aggressively trying to pull business," Guralnick, who is based in Spring Mills, Pa., said.

The manufacturing, research and development facility will be part of the global launch of the world's first tablets intended to reduce a person's sensitivity to allergens, ALK-Abello said.

According to the World Health Organization, up to 25 percent of the population in the United States, Europe and Japan suffer allergies. Most are treated with symptom-relieving medications.

While immunotherapy can alter an allergy, only a few people receive such treatment because it typically involves receiving 25 to 50 injections of the immunotherapy product.

The company believes the development of tablets will make such immunotherapy much more popular. ALK-Abello, based in Horsholm, Denmark, currently has four products in its pipeline, targeting grass pollen, house dust mites, ragweed and birch allergies.

The tablet targeting grass pollen was approved in 27 European countries in 2006 and is currently being launched there.

Biopol Laboratory was founded in Spokane in the 1970s and was bought by ALK-Abello and Vespa in 1999, Guralnick said. The company's operations had been spread across five buildings in the Spokane area but will now be consolidated on 12.5 acres at the Post Falls site.

That facility, which will cover 68,000 square feet and initially employ about 50 people, is expected to be open by 2009.

Biopol also runs a 600-acre farm in nearby Plummer, Idaho, where it grows a variety of dryland grasses and other plants to produce pollens used as raw materials in the tablets.

The new facility will cover ALK-Abello's raw material needs for grass and house dust mite allergies. A second phase will include raw material for future products to treat ragweed pollen allergy, which is being developed by ALK-Abello and its U.S. partner, Schering-Plough Corp.

"This is a phenomenal company with strong wages and benefits," said Steve Griffitts, president of Jobs Plus Inc., the Coeur d'Alene Area Economic Development Corp.