Is it permissible for a person afflicted with allergies, who is harmed by the use of water, to combine prayers to avoid illness, or is it obligatory for him to perform tayammum for each prayer and offer each prayer at its appointed time?

If using water on a specific limb causes pain, it is sufficient to perform tayammum (definition) for that limb and wash the remaining limbs. However, if using water absolutely is harmful, then ablution is forfeited, and tayammum becomes obligatory for each prayer at its designated time. It is permissible to combine prayers nominally with a single ablution, such as delaying Dhuhr and bringing forward Asr, or delaying Maghrib and bringing forward Isha. However, it is not permissible to delay a prayer beyond its time or to perform it before its time.