Generally speaking, fear is rational and when it becomes irrational it changes into a phobia.  It's subjective, mainly because it's one of degree.  The easiest way to determine what you might have is to judge if it's more irrational than rational or not.  Every fear uses our imagination which is powerful and therefore always have some amount of irrationality.

Social Phobia  is certainly the single most common cause of problem that is treated here.

Social phobia revolves around a fear of how others might see you, what they think of you, and feeling that whatever you’re doing is getting noticed.

The fear of being judged.

In essence, social phobia is a fear of being judged.

If you suffer from social phobia / social anxiety, this fear becomes your own worst enemy.
 

The symptoms of social phobia (social anxiety).

The symptoms produced by this condition can vary from ...

• · dry mouth
• · blushing
• · feeling sick
• · shaking
• · feeling weak
• · shy bladder (inability to urinate in public toilets)
• · stammering
• · diarrhoea
• · stuttering
• · sweating
• · having palpitations.

• ...Ultimately, it can cause a full-blown anxiety or panick attack. Social anxiety also shares many similar symptoms with general anxiety.

Social situations

The fear of social phobia  is based around social / public situations, and these can range from anything such as nights out, to going shopping, meeting people, going to work, parties, entertainment situations, or even a complete inability to use public toilets (shy bladder), as well as many other situations where people come into some kind of contact with others.

Avoidance.

Indeed, they may arrange their whole life to avoid situations where social interactions may occur.

This can include avoiding using / answering the telephone, or typing / writing something down in front of others, avoiding signing their name, or indeed anything that could possibly put them at the centre of attention, or 'on the spot'.