1 - Active Breathwork implies Conscious Connected Breathing, any session can lead you to experience some psychological changes, your body might get into intense physical and you might release emotional waves.
2 - Some of the effects you might feel uncomfortable with :

   ⊛ Tingling sensations 
   ⊛ Dizziness
   ⊛ Trembling, shaking, muscular cramp, other physical sensations
   ⊛ Emotional experience

   ⊛ Energy flow sensation through the whole body

As per professional recommendations, hereby the conditions as listed contraindicated for anyone considering Active Breathwork : 

    ⊛  Certain stages of Pregnancy are not recommended as early stage and late stage :
         Time period you might not practice Active Breathwork : before the 4th month and after the 7th month time
    ⊛  Eye Condition : Detached Retina and Glaucoma
    ⊛  High Blood pressure Condition which is not monitored with medical treatment
    ⊛  Cardiovascular Condition, previous stroke or heart attack, including heart angina
    ⊛  Diagnosed Aneurysm ( Brain, Abdomen ... )
    ⊛  Respiratory Issues as Severe Asthma Condition
    ⊛  Epilepsy, Seizures 
    ⊛  Prior diagnosis of Bipolarity Disorder, Schizophrenia or Serious Psychiatric Condition
    ⊛  Clinical Hospital Admission for any psychiatric condition or emotional distress within the last 7 years time
    ⊛  Any Emotional, Psychiatric, Physical Condition which might impair or affect the ability to engage in activities
         involving intense physical and/or emotional release