The idea of consent when first aid is required is a little more complicated than a simple yes or no. Everyone has the right to refuse care so getting consent is very important but there are circumstances where you can perform first aid without verbal consent. This is the where difference between expressed and implied comes in.
Consent to treatment means a person must give permission before receiving any kind of medical treatment, test or examination. Physically touching someone who does not want your help could be considered assault.
According to the NHS, for consent to be considered valid it must be; voluntary and informed, and the person giving it must have the capacity to do so.
Voluntary - the person must make the decision on their own with no input from medical staff, family or friends.
Informed - they must have all the information possible
Capacity - they must be capable of giving consent, which means they understand and can use the information to make an informed decision.
If an adult conforms to all of the above, their decision must be respected even if their decision could result in more damage or even death to themselves or their unborn child.
If a person does not have capacity or some who can speak for them the medical professionals can provide treatment if they believe it is in the person's best interest.
Consent can be expressed verbally or in writing. Someone could give non-verbal consent if they fully understand the treatment, eg holding out an injured arm for a bandage.
Simply put, expressed consent is the person telling you it is okay to provide assistance
Consent from children and young people
If they are able to, consent is usually given by the patient themselves but someone with parental responsibility may need to consent to children up to the age of 16 to have treatment.
When consent is not necessary (Implied)
There are a few exceptions where it is not necessary to get the person's consent. Several of them do not apply when considering First Aid (eg needing an additional emergency procedure during an operation). The one we need to know is that if they need emergency treatment to save their life but they are incapacitated, eg unconscious, intoxicated, don't speak the same language... we can administer First Aid - once they have recovered, the treatment and the reason for the treatment will need to be explained to them.
With implied consent it is assumed that the person would ask for help if they could.