Carers allowance is a benefit available to you if you care for someone for at least 35 hours a week (you do not get paid extra if you care for more than one person. If someone else also cares for the same person as you, only one of you can claim Carer’s Allowance). The current rate for Carers Allowance is £69.70 a week. To be eligible for carers allowance you must care for your child for at least 35 hours a week and the child must be in receipt of the middle or highest rate care component of Disability Living Allowance.
You can only claim if your income after Tax, National Insurance and Expenses (like pension contributions) is £132 a week or less.
For more details see: https://www.gov.uk/carers-allowance
If you're on Universal Credit, claiming Carers Allowance will affect your Universal Credit. The general principles are:
Your Universal Credit payment will be reduced by an amount equal to your Carers Allowance payment.
If your child is disabled you'll be eligible for an extra amount of £132.89 per month or £414.88 if your child is severely disabled.
If you care for someone who gets a health or disability benefit (eg. DLA) for at least 35 hours a week you'll get an extra monthly payment of £168.81