Primary hyperalgesia is sensitization of bare nerve endings and secondary hyperalgesia is sensitization of encapsulated nerve endings

Primary hyperalgesia is sensitization of the damaged area to non-painful stimuli and secondary hyperalgesia is sensitization of the damaged area to painful stimuli 

Primary hyperalgesia is sensitization of the damaged area and secondary hyperalgesia is sensitization of surrounding skin

Primary hyperalgesia is due to sensitization of TRPV1 channels and secondary hyperalgesia due to sensitization of voltage-gated channels

Primary hyperalgesia is sensitization of the damaged area to painful stimuli and secondary hyperalgesia is sensitization of the damaged area to non-painful stimuli