Witnesses to acid attacks are being told how they can help victims as the number of assaults with corrosive substances continues to rise.
Victims can be left blind or severely disfigured and the minutes after an attack are critical in helping those affected, health officials at NHS England said.
The three Rs:
Report - dial 999 to call emergency services
Remove - carefully remove contaminated clothing, ideally cutting it away. Be careful not to spread the acid, especially onto the victim's face - or onto yourself
Rinse - immediately rinse the skin under running water
NHS England has shared the advice with emergency responders including police and ambulance personnel so they know what to do if they are called to the scene of a corrosive substance attack.
The new guidance comes as health officials have noted a rise in the number of people in England requiring specialist help for this type of assault.
In 2014, 16 people required specialist medical advice, rising to 25 in 2015 and 32 last year, NHS England said.
The number of people requiring help from specialist burns units - where the most severe cases are treated - is expected to rise further this year.
Victims whose injuries are not as severe can be treated and discharged by doctors in emergency departments.
More than 400 acid or corrosive substance attacks were carried out in the six months up to April this year, according to figures from 39 police forces in England and Wales.
Working with the British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS), NHS England has also created an online tool offering guidance and support to victims and their families.
Professor Chris Moran, national clinical director for trauma at NHS England, said: "Whilst this type of criminal assault remains rare, the NHS is caring for an increasing number of people who have fallen victim to these cowardly attacks.
"One moment of thoughtless violence can result in serious physical pain and mental trauma, which can involve months if not years of costly and specialist NHS treatment.
"So-called acid attacks are medical emergencies and people should immediately dial 999. We are issuing guidance today that sets out clearly and simply how people can help themselves and others in response to attacks.
"Our guidance will outline what first steps to take in the event of an attack in those crucial minutes before professional clinical help arrives on the scene."
BAPRAS president David Ward said: "Surgeons specialising in burns and trauma have seen first-hand the devastating impact on patients admitted to A&E after vicious corrosive substance attacks. They cause severe pain, scarring which can be life-long, and can damage the sight, sometimes leading to blindness.
"Unfortunately these vindictive attacks are on the increase.
"The minutes after an acid attack are critical for helping a victim. This guidance BAPRAS has published with NHS England gives the important, urgent steps a victim or witness can take to help reduce the immediate pain and damage, and long-term injuries."
NHS England has estimated that the average cost of care for victims requiring specialist burns treatment, eye care, rehabilitation and mental health treatment is £34,500.