RAS can occur at any age. It is most common in toddlers, who usually grow out of it. However, it can reoccur in adolescence and adulthood as "cardio-inhibitory neutrally mediated syncope".
Any unexpected pain, fear, fright or surprise can trigger an attack. During the RAS the heart stops, and typically the eyes roll, there is a deathly pallor (paleness) and clenching of the jaw. The body can stiffen, breathing becomes shallow or stops, and there may be jerking movements of the arms and legs.
After a few seconds to half a minute, the heart starts beating again and the body relaxes. The child may remain unconscious for a few minutes to a few hours afterwards, in a deep sleep.
The frequency of attacks varies, and most will have some attacks that seem unprovoked. They look frightening but are not life-threatening.