Technology guide
The biphasic effect in HIFU: understanding and avoiding the risk
More HIFU does not give a better result: beyond a certain dose, the skin can become lax instead of firmer. What the biphasic effect is and how to guard against it.
The paradox
In HIFU, the dose response is not linear. At an appropriate dose, well-spaced thermal points trigger contraction and collagen production that firm the skin. At an excessive dose, the skin can instead become lax: this is the biphasic effect.
What happens in the event of excess
When the thermal points are too close together or too numerous, they merge and form a continuous zone of damage. Healing becomes excessive and disorganised: the tissue loses its elasticity, may contract irregularly and then take on a lax appearance.
Rules of caution
Respect the number of shots and the spacing set out in the protocol, limit the number of passes over the same area, do not shorten the interval between two shots, and space sessions several weeks apart to allow the skin to heal. After a full series, wait for the results to mature before considering a touch-up.
Warning signs
Redness lasting several days, marked swelling, irregular texture or folds, an unusual tight feeling: suspend the sessions and refer the client to a doctor if necessary.
What the UltraLift III does
According to the manufacturer, the protocols built into the UltraLift III software automatically adjust the number of shots and the power per area, precisely to avoid this effect. Training remains essential.
The message for the client
HIFU works by triggering natural healing: the result builds up over several months. Increasing the number of sessions does not speed it up and may compromise it.