What happens to a person if head lice is never treated?

Itching infection. They will spread throughout the head amd cause itching, secondary infected scalp and swollen gland. When extensive it may require cutting off the hair to eradicate the infection.
Head Lice. Lice will not go away without treatment. If the initial treatment does not kill all of the eggs (nits), a follow-up treatment may be required 7 to 10 days later to kill the newly hatched lice. Itching may last for 7 to 10 days even after successful treatment.