Police departments in the United States are reported to have bought a foul-smelling liquid developed in Israel to repel protesters. What is "skunk" and how is it used, asks Yolande Knell.
It is a truly putrid stench. Palestinians who have been sprayed describe it as "worse than raw sewage" and "like a mixture of excrement, noxious gas and a decomposing donkey".
Invented by Israeli firm Odortec, skunk water was first used by the Israeli military against demonstrators in the occupied West Bank in 2008. Since then armoured vehicles equipped with water cannon spraying jets of the stinky liquid have become a regular sight.
Although it may induce a gagging reflex, the company says skunk is made from "100% food-grade ingredients" and is "100% eco-friendly - harmless to both nature and people".
The secret recipe includes yeast, baking powder and water, which sounds innocent enough. But the scent can linger on skin and in the environment for days, sometimes longer.
"Once I was trapped against a wall and covered head to toe in skunk," a Palestinian photographer says.
"Afterwards my car stank and my wife made me undress outside the house. One of my cameras was destroyed and the rest of my kit still smells."
A spokesman for the Israel Defense Forces (IDF) told the BBC that skunk is "an effective, non-lethal, riot dispersal means" that can reduce the risk of casualties. The police, too, describe it as a "humane" option.
Tear gas and rubber bullets are regularly used against angry crowds, and sometimes even live ammunition.
"The police deal with an important ethical question: is there a need to hurt a fiery crowd in order to disperse it?" says spokeswoman, Luba Samri.
"By choosing to use this tool, the answer is clear and the ethical problem is solved as there's no need to hurt the protesters even if they act violently."
Israeli security forces have been accused of misusing the stinking liquid.
Last year police sprayed large quantities of it in East Jerusalem neighbourhoods, at a time of widespread unrest.
The Association for Civil Rights in Israel complained that this was "disproportionate", affecting the lives of tens of thousands of Palestinians.
It documented cases where homes, shops and schools were hit with the foul liquid long after rioters had left the area.
In the West Bank village of Kafr Qaddum, skunk has been used to break up weekly rallies against Israel's closure of a nearby road. The protest organiser claims his home has also been singled out.
"Several times they purposefully targeted my house," says Murad Ishtewe. "Once the high pressure of the jet broke the window so the water came inside. All my furniture was ruined."
The IDF said it was not aware of such an incident.
"For us it's a complex picture," says Sarit Michaeli of the Israeli human rights group, B'Tselem.
"The authorities ought to find non-lethal ways of maintaining law and order. The problem is the way skunk is used. Very often it is a form of collective punishment for a whole area."
Many Palestinians view the offensive smell as a humiliation, as skunk is used almost exclusively against them. Exceptions are rare. One came in April this year, when it was sprayed (possibly diluted) at Ethiopian-Israelis protesting against what they saw as racially motivated police violence.
The American firm, Mistral Security, which supplies skunk in the US, recommends it for use at "border crossings, correctional facilities, demonstrations and sit-ins".
It offers canister rounds and grenades as well as a special soap to counter the effects.
Several US police departments, including the St Louis Metropolitan Police, are reported to have bought it.
But some American commentators have warned that the use of a faecal-smelling substance in recent US riots would only have intensified anger against the police, and deepened racial and social divisions.
If officers are accidentally sprayed with their own skunk, they can neutralise the smell with the special soap.
Members of the public do not have this option. However, one photographer says tomato ketchup serves as an antidote. If you rub a surface that has been exposed to skunk with ketchup, and then wash it off, the smell will apparently become fainter.
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