Spring has come - and with it, teary eyes and runny noses for those with hay fever, as pollen is released into the air with each gust of wind that comes with the change in seasons.
This is the start of the peak sales season for surgical masks in Japan, which help to alleviate the cold-like symptoms of pollen allergy.
Anyone visiting the country at this time of the year will find it hard to walk on the streets and not meet anyone wearing a mask.
But if you stay in Japan long enough, you would realise that the Japanese love affair with the surgical masks goes beyond health and hygiene - to the realm of psychology and even pathology.
While many wear the mask as a defence against allergens, some use it as a cover-up, a shield against social situations that trigger anxiety.
Figures attest to a phenomenon some have termed "mask dependency": Mask production rose 20 per cent year on year in 2015, to a record high of 4.9 billion pieces, according to latest data from the Japan Hygiene Products Industry Association.
Year-on-year percentage increase in mask production in 2015.
Number of masks produced in 2015, a record high.
Percentage increase in number of mask addicts seeking counselling at a clinic in recent years, compared with in 2009.
Total sales nationwide tallied 23.2 billion yen (S$294 million) in 2014, said marketing consultant firm Fuji Keizai. When the H1N1 flu epidemic broke out in 2009, sales peaked at 34 billion yen.
NOTHING TO SNEEZE AT
Around one in three of Japan's 127 million people suffers from hay fever, according to a Ministry of Health, Labour and Welfare survey.
The volume of pollen in the air is nothing to sneeze at - pollen from over 60 types of plants and trees, such as the Japanese cedar and cypress, are linked to hay fever.
Leading mask maker Unicharm was the first hygiene products supplier to offer disposable, pollen- blocking masks in 2003, and after the outbreak of Sars in the same year, developed masks it claimed could prevent cold.
Before that, masks were mainly reusable ones made of cotton, with a replaceable gauze filter.
Mr Kikuo Tomioka, a Unicharm spokesman, said: "Our masks are fitted with filters that can keep out pollen, viruses or air polluting PM2.5 fine particulate matter, and are designed for a snug fit."
Since wearing a mask when one has a cold or flu is a socially-approved act of consideration for others, as well as a safeguard against viruses and allergens, disposable masks that were cheap and considered more hygienic proved to be the game changer.
Nearly one in three Japanese wore masks every day in 2011, compared with around one in five in 2008, according to a survey by Kobayashi Pharmaceutical, a leading maker of pollution-related face masks.
For many people, especially women, masks are for days when they feel less attractive.
"I wear masks on days when I don't have time to put on make-up before going out," said Ms Mai Hashimoto, a business marketing officer in her 30s.
She goes through about a dozen masks every two weeks.
"Now, there are many types of masks to choose from, such as those that can make your face look smaller, and they also come in various colours, which is nice," she added.
Mr Eiji Takahashi, a salesman in his 40s, said he started wearing masks regularly about five years ago.
"During the dry winter months, I found that wearing masks helped to keep my throat moisturised. It also keeps my face warm when I'm outdoors," he said.
"Now, it's become a habit."
Major pharmacies stock at least five to six different types of masks at any one time.
Unicharm's Mr Tomioka said the company has 11 types of masks - from "3D" masks that stand away from the face and masks that make one's face look smaller, to masks with aroma, like mint-scented ones, with various levels of textures for ease of wearing.
On the market, there are even pink masks for ladies and black ones for men.
Since 2012, some matchmaking companies have even started offering speed dating where participants are required to wear surgical masks. The purported aim is to encourage participants to get to know their would-be sweethearts without judging each other first by looks.
Such matchmaking events have proven to be a hit and have spread all over Japan.
The spokesman for a Tokyo-based organiser, Mask Matchmaking, said: "Wearing masks sometimes makes it hard to hear what the other person is saying, so naturally, people draw nearer to each other."
But for some Japanese, wearing masks has become an addiction.
Mr Yuzo Kikumoto, who set up professional counselling service Kikiwell in 2006, was the first to coin the term "mask dependency" in a paper he wrote in 2009.
People were wearing surgical masks not for the purposes they were intended for, he wrote, but because they had grown used to living behind the anonymity of a mask.
The situation has got even more serious in recent years, Mr Kikumoto told The Straits Times.
The number of mask addicts seeking counselling at his practice has increased by 50 per cent since 2009, he said.
Sufferers are mostly in their 30s to 40s, with women making up slightly more than half of the number , or 60 per cent.
"While some people used to feel safe or secure when going out with a mask, it has reached a stage where they cannot go out without wearing a mask. That's how serious it is getting," said Mr Kikumoto, who is a frequent guest on local TV talk shows and news programmes.
The reason for mask dependency, he said, is a feeling of insecurity in public, exacerbated by the proliferation of social media. Many who use social media frequently have become more self-conscious and crave the praise and approval of others. Those who lack such affirmation may then suffer from a deeper sense of inferiority, he added.
"The mask acts as a security blanket, and people with this addiction cannot talk to people without wearing a face mask. And society's acceptance of interactions behind masks perpetuates such a dependency," said Mr Kikumoto.
Like any addiction, treatment needs to start with recognition and admission, he added.
"An environment or situation that requires interaction with people is also needed," he said, recommending regular exposure to social situations.