The deep perfume of olive and laurel oil hangs in the air of old Aleppo, home to an ancient soap industry that has enjoyed a renaissance since the government lifted crippling trade bans in the past five years.
Nestled among the 2,000-year-old labyrinthine streets in courtyard houses and old hotels, known as khans, are a handful of workshops that have been making the famed savon d'Alep, or Aleppo soap, by hand for hundreds of years.
But the guardians of the old tradition say greedy imitators who have begun marketing cheap industrial soap under the same name are threatening to undermine the brand in lucrative European export markets.
"European consumers are very discerning. They may fork [over] several euros for a bar that has Aleppo written on it, but they will not buy Syrian soap again if it doesn't make their skin nice," says Safouh al Deiri, a Syrian businessman who has been exporting Aleppo soap to France since the 1980s.
Mr al Deiri, who lives in Lyon, France, says Aleppo soap influenced the development of soap making in Marseille during the French occupation of Syria and neighbouring Lebanon from 1920 to 1946.
The real soap, nicknamed Aleppo's green gold, is made only from olive and laurel oil, water and sodium palmate, a natural ingredient that hardens the mixture.
The resulting block is cut by hand and left to dry for a period of six months up to three years to make it last longer. The rough look of the soap and the big square bars that weigh almost a quarter of a kilo each are its trademark.
The soap's purity and simplicity - olive oil is a natural moisturiser and laurel oil is a cleanser - contrast with modern soaps that use everything from animal fat to crushed horse bone, as well as "less noble" oils, such as palm oil or other seeds.
Demand for organic and natural products has also won the product a niche market in Europe, where many people favour it over "luxury" western soaps that have more than 20 ingredients, including some chemicals.
Business in Aleppo, which was a cosmopolitan trading hub on the ancient Silk Road, has declined since the Baath Party took over Syria nearly 50 years ago and imposed Soviet-style economic policies that drove its leading business families into exile.
Restrictions on private enterprise have eased in the past years, contributing to the city's architectural rejuvenation, a rise in tourism and efforts to market the trademark soap.
But despite the marketing drive, the five established family soap makers - Zanabili, Najjar, Fansa, Jbeili and Sabouni, which means soap maker in Arabic - remain understated and do not even have signs on their doors.
They now export most of their production, estimated at 600 tonnes a year, to Europe, South Korea and Japan, especially the high-end soap that contains 16 per cent laurel oil.
Their success has spawned scores, if not hundreds, of imitators, many of whom use chemical colouring to give the soap the green tint of laurel and olive oil.
The industrial soap sells for US$2 (Dh7.35) a kilo compared with the $16 or more for the traditional soap that its makers charge, depending on the quality of olive oil and proportion of laurel oil.
Mr al Deiri says a lack of standards could deal the Aleppo soap industry the same fate that befell its textiles, which were coveted in Europe before quality dwindled.
"There is already in France natural laurel and olive oil soap made in China. The Syrian government could help preserve the quality if it sets specifications for the savon d'Alep name," he says.
At the Zanabili workshop opposite the Osmanya mosque, owner Nabil Zanabili uses a magnifying glass to inspect a bar of soap submitted to him for an expert opinion.
"It's good quality. The olive oil is good and it has a good proportion of laurel," Mr Zanabili says after smelling the soap.
He says Aleppo has been a centre of soap making since before Jesus's time, together with Antioch in modern-day Turkey and the Palestinian city of Nablus. The Mediterranean port city of Tripoli, long part of geographical Syria, but a Lebanese city since 1920, also boasts at least one old soap house.
But even Mr Zanabili has developed a line that adds almond oil, mint and lemon oil to laurel, catering for some European and Asian tastes, although he insists that the product remains of the highest quality.
Sultana, an upmarket shop that opened in Aleppo's Jdeideh district three years ago, adds jasmine essence imported from France and has a line of laurel liquid hand soap.
Marhaf Sabouni, who traces his family's soap-making heritage back 600 years, says buying one of the established names remains a safe bet because they have not compromised their quality and reputation.
But finding the high-end product in the local market may be difficult, and discerning buyers have to find their way to workshops in the old quarters of Aleppo.
Naji Fahed, who has two soap retail shops in the Syrian capital, Damascus, stocks Fansa soap at $17 a kilo, but everything else in his shop sells at a fraction of that - because not everyone appreciates the old-fashioned qualities.
"The cheap soap burns on your skin, but it has its customers," says Mr Fahed. "A famous Syrian actress is a regular buyer from me. She buys the most awful soap and says it's the best thing for her skin."