People with disabilities people have a right to confidentiality and an employer must not disclose confidential details about them without their explicit consent.
The Data Protection Act 1998 places duties on employers to ensure confidential and appropriate handling of ‘sensitive personal data’, which includes data about a person’s health.
The Data Protection Act also gives individuals the right to see personal data and information held or processed about them, provided they request it in writing. This provision is important in accessing personal information relating to a risk assessment.
If you and your employer agree to formally let other people know about your disability (which may be a 'hidden' disability) you should sign a consent form which gives your employer permission to tell one or more named individual(s). This is to comply with the Data Protection Act.
The sickness absence data you keep and process has to comply with the Data Protection Act 1998. If an absence record contains specific medical information relating to an employee this is deemed sensitive data and you will have to satisfy the statutory conditions for processing such data.