The relatedness of an animal food protein to a human protein determines whether it can cause allergy, according to new research by scientists from the Institute of Food Research in Norwich and the Medical University of Vienna.

In theory all proteins have the potential to become allergens, but the study found that in practice the ability of animal food proteins to act as allergens depends on their evolutionary distance from a human equivalent.

WASHINGTON (Reuters) - Child care workers, home health care aides and other people who provide personal services have the highest rates of depression among U.S. workers, according to a new survey to be published on Monday.

It found that 10.8 percent of personal care and service workers and 10.3 percent of food preparation and serving workers -- both usually low-paying jobs -- experienced one or more major depressive episodes in the past year.

The least depressing careers appear to lie in architecture, engineering, the sciences and in the installation, maintenance and repair fields, the survey from the Substance Abuse and Mental Health Services Administration found.

SAN JOSE, Costa Rica (Reuters) - Emergency officials across Central America worked to clean up towns inundated by recent deadly floods and landslides, and braced for more bad weather on Sunday.

At least 20 people were killed and thousands evacuated across Central America after days of torrential rain sparked landslides and flooding.

The same weather system that killed 23 people in a Haitian village on Friday triggered a landslide that buried 14 people under mud and debris in Costa Rica.

Red Cross workers had been digging through the debris since Thursday, when about 2.5 acres (1 hectare) of land on a steep slope gave way and fell on the small town of Atenas, about 20 miles west of the Costa Rican capital.

WASHINGTON (Reuters) - Smoking may turn on some genes in the body in a permanent and harmful way, scientists said on Thursday in a study that may help explain why the risk of cancer remains high even after smokers quit.

They found many genetic changes that stop when a smoker quits, but found several genes that stay turned on for years, including several not previously linked with tobacco use.

"These irreversible changes may account for the persistent lung cancer risk despite smoking cessation," the researchers wrote in their report, published in BioMed Central journal BMC Genomics.

WASHINGTON (Reuters) - Researchers have identified a batch of genes that not only prevent cancer but slow the aging process in worms, and say they are now looking to see if the genes have the same properties in humans.

Many of the genes in the worms are already known to have counterparts in humans, and the team at the University of California, San Francisco, say they hope to better understand some of the processes that cause both aging and cancer.

Drugs that mimic the effects of these genes might help people both avoid cancer and also live longer, they wrote in Sunday's issue of the journal Nature Genetics.

TAIPEI (Reuters) - From Beijing to Tokyo, Seoul, Hong Kong and Taipei, faced-paced modern life means that tea has little appeal for Asian youth who don't have the patience to wait the 10 minutes it takes to brew tea in the traditional way.

"I don't have any time or relevant tea culture," said Becca Liu, a 25-year-old college graduate in Taipei.

"I'm more curious to know how to make coffee," she added. Determined to restore tea to its exalted status in Asia, tea lovers are trying to repackage tea as a funky new-age brew to a young generation more inclined to slurp down a can of artificially-flavored tea than to sip the real thing.

SAN FRANCISCO (Reuters) - California Gov. Arnold Schwarzenegger has signed a bill whose backers say will better help police use shells from hand guns as evidence in criminal investigations, a spokeswoman said on Sunday.

The legislation marks a victory for gun-control activists and the second time Schwarzenegger signed one of their priority bills. In 2004 he approved a ban on private citizens owning .50 caliber rifles.

CHICAGO (Reuters) - Smiles may take a while, but a horrified expression is a sure-fire attention getter, U.S. researchers said on Sunday, based on a study of how fast people process facial expressions.

They believe fearful facial expressions make a beeline to the alarm center of the brain known as the amygdala, cuing humans to potential threats.

KABUL (Reuters) - Afghanistan, the world's biggest heroin producer, is struggling to cope with a drug problem as thousands of Afghans -- trying to cope with the traumas of war, displacement and poverty -- are becoming addicted to narcotics.

On the outskirts of Kabul, a sprawling bombed-out building that was once a centre for culture and science is home to over 100 squatters whose main concern is feeding their heroin habit.