The agency worked on the range – called Aloclair – when the brand was owned by Forest Laboratories and has been rehired by the new owner, Dexcel.
No other agency is thought to have had the work in the intervening time.
Account manager Kirsty Munro leads the business, which is overseen by associate director Cerys Evans. They report to Dexcel brand manager Jo Ebdon.
One in four people suffer from mouth ulcers, which are often caused by stress or reactions to food.
Women are more prone to them than men, so HSD’s campaign will target female-oriented print and broadcast outlets.