Doctors issued the warning after six children aged 18 months to three years were treated for eye injuries.
In each case the child had squeezed a capsule causing it to burst. Four children suffered serious eye damage when the detergent sprayed into their faces.
The popular capsules may be round or square and are designed to dissolve in the wash, releasing the detergent.
But their shape and “squishy” texture make them fascinating to children, the four doctors told The Lancet.
The team, led by Dr Noel Horgan from the Children’s University Hospital in Dublin, wrote in a letter to the medical journal: “These products are designed to be placed directly in a washing machine and since the detergent is enclosed they may appear safer. However, the tablets are of ideal size and consistency to be of interest to young children, who may instinctively squeeze them.
“Although the tablets are quite strong, they are liable to burst when squeezed hard, and in contact with water they become softer. In our patients, bursting led to detergent being sprayed over the eyes and face.”
The children were all treated at the Dublin hospital over six months.
They suffered damage to the cells lining the cornea, the “window” covering the front of the eye. Four had also sustained significant injuries to the conjunctiva, the thin transparent layer of tissue that surrounds the eye.
All were admitted to hospital and kept in for two to five days. Their injuries eventually healed, but the doctors said more serious damage may have occurred if water had not been promptly splashed over their eyes.
Washing machine detergents contain alkaline agents, which can cause the most severe form of chemical eye injury.
Alkaline chemicals are toxic to many cells found in the eye and can produce long-term damage and impaired sight.
The doctors called for action in the form of better warning labels and packaging to protect children.