Anyone who witnesses an acid attack should immediately phone 999, help the victim take off any contaminated clothing and then rinse the affected area with water, new guidelines state.
The advice, issued by NHS England and leading burns surgeons has been issued as the number of assaults with corrosive substances continues to rise.
More than 400 acid attacks were carried out in the six months to April 2017.
The attacks can leave victims blind or severely disfigured, and the minutes immediately afterwards are critical in helping those affected, health officials have said.
What to do if you witness an acid attack:
NHS England have shared the Report, Remove, Rinse advice with the emergency services, as well as the wider public, so that they know what to do if they are called to an acid attack.
While the number of acid attacks is on the rise, the number of people requiring specialist help after such an assault is also increasing too.
In 2014, 16 people required specialist medical advice, rising to 25 in 2015 and 32 last year, NHS England said, with the the number of people requiring help from specialist burns units – where the most severe cases are treated – expected to rise further this year.
Victims whose injuries are not as severe can be treated and discharged by doctors in emergency departments.
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.