Excilor Ultra is a treatment for fungal nail infections which can help to keep even extensive infections under control until your nail heals. . This extra-strong formula penetrates deep into your nail for up to 24 hours, . Helping your nail to grow back stronger and healthier with just one treatment a day. . A fungal nail infection is a common condition which happens when fungi get under your toe or fingernail and cause an infection. . They’re especially common if the area around your nails is warm and damp, for example, if you have sweaty feet after exercising. . When you have a fungal nail infection, you’ll notice your nail becoming discoloured, usually starting at the edge and spreading inwards. . If left untreated, this can make your nail brittle until it starts to break off and can come away completely.