People who don't like pets like them even less at $400 a night.

In a bid to attract pet owners, hotels have been welcoming pets in greater numbers in recent years. Nearly half of U.S. hotels accept pets, according to the American Hotel and Lodging Association's 2006 annual survey, up from about 30 percent 10 years ago. Many now offer elaborate pet-friendly perks, from "canine cocktail hours" at the Hotel Indigo chain to "rover relaxation massages" at Peninsula Hotels.

But the rising acceptance of pets in hotels is pitting the 63 percent of U.S. households that own pets against the estimated 17 percent of the U.S. population that tests positive to cat or dog allergens. As the popularity of pet programs has grown, many hotels have stopped keeping track of which rooms pets have been in.

Now, guests with allergies, asthma and pet aversions are finding themselves in beds where animals have slept the night before, or on elevators with dogs that they fear will slobber or shed on their clothes. One big issue is lack of consistent information on what rooms allow pets or where pets have stayed. Cleaning procedures for rooms that have had pets in them also vary widely. As a result, some travelers with high sensitivity are becoming amateur detectives, trying to keep track of hotels' animal policies and sniff out rooms where pets may have been ahead of time.

Janice Lichter, a retired research analyst who is extremely allergic to cats, used to go regularly to the Boca Raton Bridge Hotel in Florida. Last June, she learned it was under new management, and now pet-friendly.

"I was like, uh-oh," said Lichter. The hotel says it allows pets only on the second floor, but when Lichter called to confirm, she said the reservation agent, assuming she was a pet owner, told her, "Oh no, you can have any room you want." Lichter immediately canceled the reservation. Hotel spokeswoman Melissa Payson said the agent was mistaken.

Reliable information can be hard for guests to pin down.

Conflicting reports

A reservation agent for the Park Hyatt Washington said last month that there were "definitely" pet-free rooms available, but a hotel spokeswoman said this is incorrect: Pets are allowed in every room. Agents for the Ritz-Carlton on Central Park in Manhattan said they can request pet-free rooms for guests, but the front desk said they have no record of where pets have stayed.

This summer, Yvonne Sherrer, a rheumatologist in Fort Lauderdale, Fla., sent a letter to the head of the disability-rights division at the Department of Justice, expressing her particular concern for young children with asthma.

"In most cases, parents are not even aware that there has been animal dander exposure because hotels do not generally make it known when they allow animals in any room," wrote Sherrer. A spokesman for the Justice Department said the letter is under review.

She was disappointed to find out that the Four Seasons Resort in Jackson Hole, Wyo., where she'd been hoping to stay recently, allows pets in every room. Last year, she skipped a medical conference in New York at a Marriott for the same reason.

Some groups, such as the Asthma and Allergy Foundation of America, argue that hotels are obligated by law to keep at least a few rooms animal-free. Under Title III of the Americans with Disabilities Act, anyone who owns or operates a place of public accommodation such as a hotel or restaurant cannot discriminate against individuals on the basis of disability with regard to the full and equal enjoyment of the place. Mike Tringale, director of external affairs for the Asthma and Allergy Foundation, said this implies that every facility should offer allergen-free rooms for guests with allergies, just as they must offer ramps and large elevators for guests in wheelchairs.

Playing the disability card

Gary Phelan, a disability lawyer with the firm Outten & Golden LLP, said there's no law requiring hotels to offer pet-free rooms, but that people with severe asthma and allergies have qualified as disabled under the act on rare occasions.

The Americans with Disabilities Act defines a disability as "a physical or mental impairment that substantially limits one or more of the major life activities of the individual," and breathing is considered a major life activity, said Phelan.

American Hotel and Lodging Association President Joe McInerney said there are too many different types of allergies for hotels to accommodate everyone's specific needs.

Some 50 million Americans suffer from allergies, according to the Asthma and Allergy Foundation, and the second most common (after pollen) is to animal dander — tiny flakes of skin, hair and dried saliva that float in the air and cannot be removed by steam-cleaning carpets or hand-washing walls. For severe allergy sufferers, reactions to dander can require hospitalization — and can be life-threatening without proper medications, allergists say.

Pets have been welcome in some hotels for decades — the Four Seasons, for example, said it has always allowed guests to bring animals, provided the pets weigh less than 15 pounds. But other big chains have only recently begun to follow suit. Starwood decided to make all of its Sheraton, Westin and W hotels in the U.S. and Canada pet-friendly in 2003, after a company-commissioned study of dog owners found that 76 percent of respondents said they would be more loyal to a hotel chain that accepted dogs, even when not traveling with one.

Pettravel.com, an online travel guide for pet owners, has added almost 3,000 pet-friendly hotels this year. The list now comprises 35,484 hotels worldwide. President Jerry Hatfield, who started the list 10 years ago with about 1,500 properties, said a big reason hotel managers ask to be listed is that guests traveling with pets tend to stay longer because they're not anxious to get back to the kennel.

Some mitigation possible

Though it's impossible to eliminate pet dander, a thorough cleaning can get rid of some of it. Post-pet cleaning procedures vary widely from hotel to hotel. The Ritz-Carlton, which accepts pets at some of its domestic properties, typically charges pet owners a $150 fee (depending on the property) to cover the deep cleaning, which takes twice the length of a normal cleaning and includes shampooing the carpets and disinfecting the walls. The Park Hyatt Washington, which doesn't have designated pet rooms and offers dog beds, toys, treats and stainless-steel dog bowls, said it dry-cleans bedding in rooms after pets have stayed, replaces air conditioning filters and steam-cleans the carpets.

The Peninsula doesn't have a special cleaning routine for rooms that have housed pets — cleaning is commensurate with the condition of the room, a spokeswoman said. The Four Seasons in Beverly Hills said its housekeeping staff steam-cleans the carpets after pets instead of vacuuming, and airs out the rooms longer than normal, but that air-out time depends on how soon the room is needed for the next guest.

Starwood, which adds $25 to the nightly rate for pets and levies a $100 cleaning fee, airs out rooms for 12 hours after pets depart and purifies the air with ozone.

Yet no amount of cleaning can erase the image of animals from some picky travelers' minds. Raquel Skinner has no allergies, but the 32-year-old chemical buyer in Grand Blanc, Mich., avoids staying at pet-friendly hotels when she can: She says she simply doesn't "care for animals running around salivating where I will be sleeping."